Full text of Code of Lighting: Factories, Mills and Other Work Places : Bulletin of the United States Bureau of Labor Statistics, No. 556

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UNITED STATES DEPARTMENT OF LABOR
W. N. DOAK, Secretary

BUREAU OF LABOR STATISTICS
ETHELBERT STEWART, Commissioner

BULLETIN OF THE UNITED STATES I
BUREAU OF LABOR STATISTICS/ • • • •
SAFETY

CODE

CCC

fl|0» DDO

SERIES

CODE OF LIGHTING: FACTORIES, MILLS
AND OTHER WORK PLACES
REVISION OF 1930
AMERICAN STANDARD
Approved by the
AMERICAN STANDARDS ASSOCIATION
AUGUST 18,1930

SPONSOR
ILLUMINATING ENGINEERING SOCIETY
New York, N. Y .

October, 1931

UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON s 1931

For sale by the Superintendent of Documents, Washington, D. C«

Price 15 cents

CONTENTS
Page

Introduction____________________________________________________
Part 1.—Advantages of good illumination__________________________
Reduction of accidents_______________________________________
Economy of operation________________________________________
Part 2.—Suggestions and general information_______________________
Measurement of illumination__________________________________
Recommended levels of illumination____________________________
Natural lighting_____________________________________________
Maintaining the level of illumination___________________________
Avoidance of glare___________________________________________
Rating light sources from the glare standpoint (Table 4)_____
Factors affecting glare________________________________________
Brightness of source__________________ ____________________
Total volume of light____________________________________
Location in the field of view_______________________________
Contrast with background________________________________
Time of exposure________________________________________
Glare by reflection___________________________________________
Importance of adequate electrical wiring________________________
Specification of adequate wiring________________________________
Locating switches___________________________________________
Part 3.—Suggested minimum regulation to be established by State
authorities____________________________________________________
Purpose-------------------------------------------------------------------------------Exceptions_________________________________________________
Scope______________________________________________________
Rules------------------------------------ ------- --------------------------------------General requirement_____________________________________
Rule 1.—Illumination required____________________________
Rule 2.—Avoidance of glare----------------------------------------------Rule 3.—Exit and emergency lighting______________________
Notes on rules______________________________________________
Subject index_________________________________ _________________
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21

Illuminating Engineering Society
The Illuminating Engineering Society was organized in 1906
for the advancement of the theory ana practice of illuminating
engineering and the dissemination of knowledge relating thereto.
The society now has about 2,000 members who are interested in
the subject of lighting from various standpoints—engineering,
economic, hygienic, and esthetic.
The society has no affiliation with any commercial organization.
Anyone interested in its objects may become a member.

Note on Revision of Code
The present code was revised under the rules of procedure of,
and has been officially approved as an “American standard” by,
the American Standards Association. For this purpose it was
first submitted to and approved by a sectional committee made
up of representatives officially designated by the following societies
and organizations:
Gas A s s o c i a t i o n : W. J. SerriU, United Gas Improvement Co.,
1401 Arch Street, Philadelphia, Pa.
A m e r i c a n I n s t i t u t e o f A r c h i t e c t s : LeRoy E. Kern, technical secretary,
Structural Service Department, The Octagon. 1741 New York Avenue,
Washington, D. C.
A m e r i c a n I n s t i t u t e o f E l e c t r i c a l E n g i n e e r s : Prof. Lewis FusseU, depart
ment of electrical engineering, Swarthmore College, Swarthmore, Pa.;
Charles H. Moore, American Can Co., 120 Broadway, New York, N. Y.
A m e r i c a n S o c i e t y o f M e c h a n i c a l E n g i n e e r s : L . A. Blackburn, Oakland
Motor Car Co., Pontiac, Mich.
A s s o c i a t i o n o f E d i s o n I l l u m i n a t i n g C o m p a n i e s : G. Bertram Regar, Phila
delphia Electric Co., 1000 Chestnut Street, Philadelphia, Pa.
A s s o c i a t i o n o f G o v e r n m e n t a l O f f i c i a l s i n I n d u s t r y : Charles H. Weeks,
deputy commissioner of labor, New Jersey Department of Labor, Trenton,
N. J.
I l l u m in a t in g
E n g in e e r in g
S o c i e t y : Ward Harrison, chairman, General
Electric Co., Nela Park, Cleveland, Ohio. WilUam F. Little, secretary,
Electrical Testing Laboratories, Eightieth Street and East End Avenue,
New York, N. Y.
A

m e r ic a n

I n t e r n a t io n a l A

s s o c ia t io n o f

I n d u s t r ia l A

c c id e n t

B oards

and

C o m m is s io n s :

Thomas C. Eipper, State industrial commission, 124 East Twenty-eighth
Street, New York, N. Y.
N a t i o n a l A s s o c i a t i o n o f B u i l d i n g O w n e r s a n d M a n a g e r s : W. E. Malm, Arcade
Building, Cleveland, Ohio.
T h e N a t i o n a l A s s o c i a t i o n o f C o t t o n M a n u f a c t u r e r s : F. M. Gunby, 201
Devonshire Street, Boston, Mass.
N a t i o n a l B u r e a u o f C a s u a l t y a n d S u r e t y U n d e r w r i t e r s : R. E . Simpson,
Travelers Insurance Co., Hartford, Conn.
N a t i o n a l E l e c t r i c L i g h t A s s o c i a t i o n : Alexander Maxwell (alternate), Na
tional Electric Light Association, 420 Lexington Avenue, New York, N. Y .;
W. T. Blackwell, Public Service Electric & Gas Co., 80 Park Place, Newark,
N. J.
N a t i o n a l E l e c t r i c a l M a n u f a c t u r e r s A s s o c i a t i o n : P. C. Keller, Ivanhoe Divi
sion of the Miller Co., Meriden, Conn.

NOTE ON REVISION OF CODE

N a tio n a l S a fe t y C o u n c il

: W. Dean Keefer, 20 North Wacker Drive, Chicago,

111 .
U n it e d S t a t e s B

ureau

Standards

Washington, D. C.
U n it e d S t a t e s D

Washington,

epartm ent

: Dr.

L abor:

G. Lloyd, Bureau of Standards,

W. F. Kelley, 122 Raleigh Street

S E .,

D . C.

S t a t e s N a v y D e p a r t m e n t : W. G. Hill, Bureau of Yards and Docks,
Navy Department, Washington, D. C.
U n i t e d S t a t e s P u b l i c H e a l t h S e r v i c e : Dr. J. E. Ives, 16 Seventh Street SW.,
Washington, D. C.
U n i t e d S t a t e s W a r D e p a r t m e n t : George E. Lamb, Quartermaster Corps,
39 Whitehall Street, New York, N. Y.
M e m b e r s a t L a r g e : J. M. Woltz, safety director, Youngstown Sheet & Tube
Co., Youngstown, Ohio; N. L . Ramsey, safety engineer, Joseph Reid Gas
Engine Co., Oil City, Pa.; H. L . Miner, manager safety and fire-protection
diyision, E. I. du Pont de Nemours & Co. (Inc.), Wilmington, Del.

U n it e d

BULLETIN OF THE

U. S. BUREAU OF LABOR STATISTICS
m o . 556

WASHINGTON

O c t o b e r , 1931

CODE OF LIGHTING: FACTORIES, MILLS, AND OTHER
WORK PLACES
Introduction
The accompanying code of lighting for factories, mills, and all
other work places1has been prepared and issued by the Illuminating
Engineering Society as a guide for factory owners and operators in
their efforts to improve lighting conditions in their factories. It
makes available authoritative information for legislative bodies,
factory, boards, industrial commissions, and others who are interested
in enactments, rules, and regulations for better lighting.
Parts 1 and 2 of this code discuss the advantage oi good illumi
nation and describe the essentials of such illumination. Part 3
contains a set of regulations suggested for adoption by State
authorities.
Since the first edition of this code was issued a number of the
States of the Union, recognizing the beneficial effects of adequate
illumination on the health and safety of employees, have adopted
factory lighting regulations. These regulations stipulate the mini
mum illumination permissible for different classes of industrial
operations. They also indicate the desirable as distinguished from
the minimum illumination values and the kinds of lighting equip
ment which will avoid glare and give a good distribution of light.
The preface to the Wisconsin Industrial Lighting Code explains
as follows why the State is concerned in the regulation of factory
lighting:
Insufficient and improperly applied illumination is a prolific cause of indus
trial accidents. In the past few years numerous investigators studying the
cause of accidents have found that the accident rate in plants with poor
lighting is higher than in similar plants which are weU illuminated. Factories
which have installed improved lighting have experienced reductions in their
accidents which are very gratifying.
Of even greater importance, poor lighting impairs vision. Because diminution
of eyesight from this cause is gradual, it may take the individual years to
become aware of it. This makes it all the more important to guard against
the insidious effects of dim illumination; of glaring light sources shining in
the eyes; of flickering light; of sharp shadows; of glare reflected from polished
parts of the work. To conserve the eyesight of workers is a distinct economic
gain to the State, but regardless of that, humanitarian considerations
demand it.
Finally, inadequate illumination decreases the production of the industries
of the State and to that extent the wealth of its people. Factory managers
who have installed improved illumination are unanimous in the conviction that
better lighting increases production and decreases spoilage.
1 Revision o f original code which was approved as American Standard by American
Engineering Standards Committee, Dec. 81, 1921. Eevision approved Aug. 18, 1930.

IN D U STRIAL LIG H TIN G CODE

Part 1.— Advantages of Good Illumination
The advisability of good natural and artificial illumination is so
evident that a list of its effects may seem commonplace, but these
effects are of such importance in their relation to management that
they are worthy of careful1attention. The effects of good illumina
tion, both natural and artificial, and of bright and cheerful interior
surroundings include the following:
1. Reduction of accidents.
2. Greater accuracy in workmanship, resulting in improved quality
of goods.
3. Increased production.
4. Less eyestrain.
5. Greater contentment of the workers.
6. Greater cleanliness.
7. More order and neatness in the plant.
8. Supervision of the employees made easier.
Reduction of Accidents
The National Safety Council in its publication “Accident Facts—
1929 ” estimates the number of fatalities in the United States arising
out of or in the course of gainful employment as 24,000 for the year
1928, and also that during the same period the lost tkne noniatal
accidents reached the staggering total of 3,125,000—about 1 acci
dent for every 4 persons engaged in industry, or 1 for every 14
persons gainfully employed.
According to E. E. Simpson, of The Travelers Insurance Co.,
there is warrant for assuming that defective vision and deficient or
unsatisfactory lighting installations are contributing factors in 18
per cent of these accidents. Simple computation will show that from
these causes industry is being deprived of the equivalent of the
services of 35,000 men throughout each entire year due to the lost
time nonfatal accidents, and that the accepted actuarial methods of
evaluating fatal accidents will bring the total loss to 125,000 men
annually. This is indeed a high price to pay for neglect of light and
vision.
That these conditions could exist year after year is all the more
reprehensible because of the fact that the remedy is so easily ap
plied and has beneficial results in many ways other than the safety
involved. Accidents caused by carelessness, inattention, or igno
rance can be eliminated only by a long-continued painstaking edu
cational campaign, often involving a change in long-established
habits. On the other hand, elimination o f accidents due to in
adequate or improper lighting is simply a matter of purchasing
the proper equipment, installing and operating it under competent
direction. In fact, it seems logical to include adequate illumina
tion in the list of safeguards, for the reason that lamps and re
flectors act as a guard because the resultant illumination points out
the hazards and aids in avoiding them just as effectively as a rail
ing points out the danger of and provides protection against the
hazard of a revolving flywheel.
Compensation-insurance premiums for a plant are based on the
amount of the pay roll, and the rate is determined by the accident

IN D U STRIAL LIG H T IN G CODE

experience of a given industry, modified by the experience of the
particular plant under consideration. With a rate of 1y2 per cent
the annual premium in the case of 1,000 employees at an average
wage of $40 per week would be $31,200.
An insurance carrier might on an average pay the claims re
sulting from four accidents per month in this plant and meet its
own overhead costs, and still have a slight margin of profit. An
experience of five accidents per month, one-fifth of them due to
improper lighting (a not unlikely event), would probably leave the
insurance carrier no option but to increase the rate by 25 per cent.
The premium would then be $39,000—an increase of $7,800. If poor
lighting costs only $3 per employee, or $3,000 per year total, the
owner’s annual expense for poor illumination actually amounts to
$10,800, of which $7,800 is required by the insurance company
to meet additional accident claims. An expenditure of $6 to $8 per
year per employee for more adequate illumination might save a
large portion, if not all, of the latter amount. The important point
here is the fact that the cost of accidents due to poor illumination
greatly exceeds the cost of providing adequate illumination.
Economy of Operation
While it is difficult to appraise the savings effected in increased
production and improved quality by good illumination, it by no
means follows that such savings are insignificant or unsubstantial.
The factory owner who ignores them neglects his own interests.
Other items in the foregoing list, even more difficult to value defin
itely, are none the less real: taken together, they constitute a power
ful argument in favor oi the best available illumination m the
factory.
The following estimate, conservatively based on practical condi
tions, gives an idea of the relative costs of good illumination by
artificial means, and of labor, in the factory.
Assume that the lamps are so spaced that one 100-watt incan
descent electric lamp will take care of one operator; that in this par
ticular case the lamp burns on the average 2 hours per day, 300
days per year; that the life of the lamp is 1,000 burning hours; and
that the operator works 8 hours per day, 300 days per year.
Investment:
Cost of lamp (list price)_________________________________
Cost of enameled steel reflector (list)______________________
Cost of wiring per outlet---------------------------------------------------

$0.35
2.50
8. 00

Total investment-------------------------------------------------------------

10. 85

Cost of operating per annum:
Interest on investment, $10.85 at 8 per cent_________________
Depreciation on reflector and wiring at 12y2 per cent_________
Renewal of lamp X%°A X $0.35------------------------------------------Cleaning, at 3 cents per cleaning, two per month------------------Energy at 5 cents per kilowatt hour---------------------------------------

. 87
1.31
.21
. 72
3.00

Total annual cost of maintaining good illumination: Per man
per year_____________________________________________

6.11

Cost of labor, annual wages per man per year:
Eight hours at 45 cents per hour; 8 X 300 X $0.45___________ 1,080.00
68793°—31----- 2

INDUSTRIAL, L IG H T IN G CODE

If an operator, because of the good illumination, saves—in more
production or better quality of product—the equivalent of only 3
minutes per day for 300 days, he will offset the annual cost of the
illumination. Good illumination is, relatively speaking, inexpensive,
and its introduction and maintenance are good investments on the
part of the factory owner.
These figures, illustrating the low cost of good lighting compared
with the cost of labor, also illustrate how large may be the losses
unconsciously sustained by the factory owner from the use of a poor
lighting system. An operator losing, say, 30 minutes per day loses
more than $60 per year, or about 10 times the cost of giving him
good illumination.
The factory owner, when approached by the lighting salesman,
should weigh carefully any argument in xavor of a change in his
lighting system which is based solely upon a resultant saving in
energy consumption. The example given above shows how greatly
the gain in increased output, due to good lighting, overbalances any
possible saving in energy consumption effected by changes in the
system of illumination. If the proposed new system sacrifices any
thing in the quality of illumination, or if it merely substitutes one
inadequate system for another, it should be rejected, and the factory
owner should insist that if his lighting installation is changed the
new system must meet the requirements of good illumination, even
thougn this involves the consumption of more energy than before.
First, a good lighting system, and then as much economy in energy
consumption as is consistent with the illumination requirements—
such a policy is the wise one for the factory owner.

Part 2.— Suggestions and General Information
Measurement of Illumination
The foot-oandle is the unit of illumination, in terms of which light
ing requirements are specified. A general idea of the amount of
illumination represented by foot-candle values can be obtained by
holding a newspaper at different distances from a bare 25-watt tung
sten filament lamp so that the light rays fall perpendicularly upon
the surface. For 16 foot-candles the distance should be 15 inches;
for 8 foot-candles, 21 inches; for 4 foot-candles, 2y2 feet; for 1 footcandle, 5 feet; for one-fourth foot-candle, 10 feet.
In this connection it should be realized that the brightness of
the surface will depend not only upon the foot-candles of incident
illumination but also upon the nature of the surface. That is, with
equal illumination, white paper will be much brighter than cast iron.
Tt is impractical and frequently misleading to attempt to estimate
foot-candle values simply by viewing an illuminated surface. The
simplest instrument for measuring these values is a foot-candle meter
(see fig. 8), with which foot-candles can with a little practice be read
accurately enough for ordinary purposes.
Points at which measurements should be taken.—In checking rec
ommended or required intensities of illumination with an instrument
such as the foot-candle meter, it is extremely important that the

IN D U ST R IA L L IG H T IN G CODE

measurement be made at the point and in the plane where the given
illumination is needed. Thus, for any operation the illumination
should be measured on the plane on which the work or operation is
performed, whether it be horizontal, vertical, or at some intermediate
angle. The illumination over an area such as a hallway or aisle
refers ordinarily to the floor level and is measured in the horizontal
plane.
Recommended Levels of Illumination
Table 1 gives the range of illumination values that are considered
desirable for different classes of work. These values are based upon
practice established through years of experience. Persons of ad
vanced years or with defective eyesight require more light than do
those having perfect vision. A range of foot-candle values is given
for each group of operations; in modern practice it will usually be
found desirable to select values in or even beyond the upper portion
of the range.
It is recognized that any specified process when carried on in dif
ferent factories is performed with different degrees of fineness and
with other variations, so that one factory may need more illumination
than another for the same class of work. In the table, ranges of
foot-candle values are given to correspond to the variations actually
existing in practice.
Attention is called to the fact that the values in Table 1 are operat
ing values; that is, they apply to measurements of the lighting system
in ordinary use, not simply when the lamps and reflectors are new
and clean.
T able

1.— Recommended levels of illumination for industrial interiors

Class of work

Aisles, stairways, passageways...................
Assembling:
Rough....................................................
Medium_______________ ___________
Fine......... ................. ......... .................
Extra fine........................................ ......
Automobile manufacturing:
Automatic screw machines...................
Assembly line........................................
Frame assembly....................................
Tool making..........................................
Body manufacturing—assembly, fin
ishing, and inspecting........................
Bakeries.......................................................
Bookbinding:
Folding, assembling, pasting, etc------Cutting, punching, and stitching-----Embossing.............................................
Candy making.............................................
Canning and preserving..............................
Chemical works:
Hand furnaces, boiling tanks, station
ary driers, stationary or gravity crys
tallizing...............................................
Mechanical furnaces, generators and
stills, mechanical driers, evaporators,
filtration, mechanical crystallizing,
bleaching............................................
Tanks for cooking, extractors, perco
lators, nitrators, electrolytic cells____

Footcandles
recom
mended
3-2
8-5
12-8
20-12

100-25
15-10
15-10
12-8

20-12
100-25
12-8
8-5
12-8
15-10
12-8

12-8

5-3

6-4
10-6

Class of work

Clay products and cements:
Grinding, filter presses, kiln rooms___
Molding, pressing, cleaning, and trim
ming____________________________
Enameling.............................................
Color and glazing_____ _____________
Cloth products:
Cutting, inspecting, sewing—
Light goods................................ .
Dark goods.....................................
Pressing, cloth treating (oil cloth,
etc.)—
Light goods....................................
Dark goods.....................................
Coal breaking and washing, screening........
Construction—Indoor general....................
Dairy products............................................
Electric manufacturing:
Storage battery, molding of grids,
charging room................................... .
Coil and armature winding, mica work
ing, insulating processes................... .
Elevator—Freight and passenger.............. .
Engraving....................................................
Forge shops and welding............................ .
Foundries:
Charging floor, tumbling, cleaning,
pouring, and shaking out................. .
Rough molding and core making..........
Fine molding and core making............ .

Footcandles
recom
mended

5-3
8—5
10-6
15-10
15-10
100-25
12-8
20-12
5-3
5-3
12-8

10-6
20-12
8-5
100-25
10-6
8-5
10-6
15-10

IN D U ST R IA L L IG H T IN G CODE
T a b l e 1 .— Recommended

levels of illumination for industrial interiors— C o n td .

Class of work

Garage—Automobiles:
StorageDead__________ ___ _____ . . . . . . _
L i v e ...............................................
Repair department and washing__....
Glass works:
Mix and furnace rooms, pressing and
lehr, glass-blowing machines..............
Grinding, cutting glass to size, silvering.
Fine grinding, polishing, beveling, in
spection, etching and decorating........
Glass cutting (cut glass), inspecting fine.
Glove manufacturing:
Light goods—
Cutting, pressing, knitting...........
Sorting, stitching, trimming, and
inspecting____________________
Dark goods—
Cutting, pressing, knitting, sort
ing, stitching, trimming, and
inspecting..........
Hat manufacturing:
Dyeing, stiffening, braiding, cleaning,
and refining—
Light...............................................
Dark__________________________
Forming, sizing, pouncing, flanging,
finishing, ironing—
Light...............................................
Dark__________________________
SewingLight...............................................
Dark__________________________
Ice making—Engine and compressor room.
Inspecting:
Rough_____________________________
M edium ..__ . . . . . . . ___ - ____ . . . . . . . .
Fine.......................................................
Extra fine_________________________
Polished surfaces.*
Jewelry and watch manufacturing............
Laundries and dry cleaning.____________
Leather manufacturing:
Vats.......................................................
Cleaning, tanning, and stretching.. __
Cutting, fleshing, and stuffing_______
Finishing and scarfing__________ ____
Leather working:
Pressing, winding, and glazing—
Light...............................................
Dark________________ ______ ___
Grading, matching, cutting, scarfing,
sewing—
Light__________________________
Dark.......................................... ....
Locker room s.... . . . . . __ . . . __ ___ ____ _
Machine shops:
Rough bench and machine work.........
Medium bench and machine work,
ordinary automatic machines, rough
grinding, medium buffing and
polishing.............................................
Fme bench and machine work, fine
automatic machines, medium grind
ing, fine buffing and polishing.........
Extra fine bench and machine work,
grinding (fine work)_______________
Meat packing:
Slaughtering........................................
Cleaning, cutting, cooking, grinding,
canning, packing_________________
Milling—Gram foods:
Cleaning, grinding and rolling___ . . . .
Baking or roasting__________ . . . . . . . .
Flour grading........................................

Footcandles
recom
mended

3-2
8-5
15-10
10-6
12-8
15-10
50-15
12-8
15-10

100-25

10-6
15-10
12-8
15-10
15-10
100-25
10-6
10-6
15-10
25-15
100-25
100-25
12-8
5-3
6-4
10-6
15-10
12-8
15-10
15-10
100-25
6-4
10-6

15-10
20-12
100-25
8-5
12-8
8-5
12-8
25-15

Class of work

Offices:
Private and general—
Close work_____ ___ ___________
No close work__________________
Distribution of mail in post offices____
Drafting room______________________
Packing:
Crating____________________________
Boxing____________ . . . . . . __________
Paint manufacturing_______________. . . . .
Paint shops:
Dipping, spraying, firing......................
Rubbing, ordinary hand painting, and
finishing_________________________
Fine hand painting and finishing..........
Extra fine hand painting and finishing
(automobile bodies, piano cases,
etc.)_____________________________
Paper-box manufacturing:
Light......................................................
Dark______________ _______________
Storage of stock____________________
Paper manufacturing:
Beaters, machine, grinding__________
Calendering________________________
Finishing, cutting, and trimming____
Plating.............................................. ...........
Polishing and burnishing_______________
Power plants, engine rooms, boilers:
Boilers, coal and ash handling, storage
battery rooms___ _________________
Auxiliary equipment, oil switches, and
transformers_____________________
Switchboard, engines, generators,
blowers, compressors______________
Printing industries:
Matrixing and casting, miscellaneous
machines, presses_________________
Proofreading, lithographing, electro
typing___________________________
Linotype, monotype, typesetting,
imposing stone, engraving____
Receiving and shipping_________________
Rubber manufacturing:
Calenders, compounding mills, fabric
preparation, stock cutting, tubing
machines, solid tire operations,
mechanical goods, building, vulca
nizing___________________________
Bead building, pneumatic tire building
and finishing, inner tube operation,
mechanical goods trimming, tread
_______
__ ___
ing
Sheet-metal works:
Miscellaneous machines, ordinary
bench work_____________________
Punches, presses, shears, stamps,
welders, spinning, fine bench work..
Tin plate inspection..... ........................
Shoe manufacturing:
Hand turning, miscellaneous bench
and machine work........................... .
Inspecting and sorting raw material,
cutting, lasting and welting (light)..
Inspecting and sorting raw material,
cutting, stitching (dark)___________
Soap manufacturing:
Kettle houses, cutting, soap chip and
powder__________________________
Stamping, wrapping and packing, fill
ing and packing soap powder............
Steel and iron mills, bar, sheet and wire
products:
Soaking pits and reheating furnaces...
Charging and casting floors__ . . . . . . . . .

*Usually require glint reflections from specially located light source.
* Special glint lighting recommended.

Footcandles
recom
mended

15-10
10-8
15-10
25-15
6-4
10-6
10-6
8-5
12-8
15-10
100-25
10-6
12-8
5-3
6-4
10-6
12-8
8-5
12-8
5-3
8-5
10-6
12-8
1&-10
100-25

6-4

12-8

M-10
12-8
15-10
* 25-15
12-8
15-10
100-25
8-5

10-6
3-2
6-4

IN D U ST R IA L L IG H T IN G CODE
T ab l e 1 . —Recommended

levels of illumination for industrial interiors—Oontcl.

Class of work

Steel and iron mills, etc.—Continued.
Muck and heavy rolling, shearing
(rough by gage) pickling and clean
ing_____________________ _________
Plate inspection, chipping-.................
Automatic machines, red, light and
cold rolling, wire drawing, shearing
(fine hy line)__________
Stone crushing and screening:
Belt conveyor tubes, main-line shaft
ing, spaces, chute rooms, inside of
bins,.___________________ ________
Primary breaker room, auxiliary
breakers under b in s .____ _______
Screen rooms_________ _____ ________
Store and stock rooms:
Rough bulky material______________
Medium or fine material requiring care.
Structural-steel fabrication______________
Sugar grading._______________ __ ______
Testing:
Rough_________ ___________________
Fine.......................................................
Extra fine instruments, scales, etc____
Textile mills:
C ottonOpening and lapping, carding,
drawing-frame, roving, dyeing..
Spooling, spinning, drawing-in,
warping, weaving, quilling, in
specting, knitting, slashing
(over beam end)__ ___________

Footcandles
recom
mended

&-5
25-15
12-8

3-2
6-3
8-5
3-2
8-5
10-6
25-15
8- 5

15-10
100-25

8-5

12-8

Class of work

Textile mills—Continued.
S ilk Winding, throwing, dyeing...........
Quilling, warping, weaving, and
finishing—
Light goods_________________
Dark goods_________________
Woolen—
Carding, picking, washing, and
combing_____________________
Twisting and dyeing____________
Drawing-in, warping—
Light goods_________________
Dark goods_________________
W eavingLight goods_________________
Dark goods_________________
Knitting machines__________
Tobacco products:
Drying, stripping, general___________
Grading and sorting________________
Toilet and wash rooms_________________
Upholstering:
Automobile, coach, and furniture____
Warehouse____________________________
Woodworking:
Rough sawing and bench work_______
Sizing, planing, rough sanding, me
dium machine and bench work, glu
ing, veneering, cooperage..................
Fine bench and machine working,
fine sanding and finish_____________

Footcandles
recom
mended

12-8
15-10
20-15
04
10-6
10-6
15-10
12-8
20-12
15-10
3-2
25-15
6-4

15-10
3-2
8-5
12-8
15-10

Where the higher levels are specified for particular processes such
illumination need not be supplied in all parts of a room, nor on all
parts of a machine, but only at locations where work of the type
indicated is likely to be performed. Thus, in a workroom, a general
illumination providing the value specified for aisles and passage
ways or storage spaces might be supplemented at proper locations
by higher illumination, specified for work of different degrees of
fineness in the table. The high illumination may be required over
small areas only, as in watchmaking and machine sewing, or over
wide areas, as in automobile assembly and finishing. In practice
the lower values required in the room will often be considerably
exceeded, in order to provide conveniently for the higher values.
The latter is fortunate, since it avoids the possibility of having ex
treme contrasts between the actual working area ana the surround
ings. (See p. 13.)
Natural Lighting
It is of interest to note that the range of illumination under which
the eye can function with some degree of success is extremely wide,
varying from a few hundredths of a foot-candle in the moonlight
up to as much as 10,000 foot-candles out in the sunlight on a clear
day. In planning a new factory building or other work place the
design should be such that the foot-candle values for daylight
should be at least twice those stated in Table 1. The natural light
ing is frequently many times these figures; in fact, illuminations of
a hundrea foot-candles or more can be measured near the window
in almost any shop. However, wide extremes in illumination are

INDUSTRIAL. L IG H T IN G CODE

not conducive to best vision. The window openings should be so
designed as to admit the greatest amount of light possible without
producing objectionable glare.
Factory owners in most industries are particularly interested in
making the best possible use of their daylight facilities, so as to
render useful and valuable all parts of the floor space, and also to
shorten the period when artificial lighting is needed. The saw
tooth, monitor, or skylight windows of modern factory construction
(fig. 5) permit of an adequate and more uniform daylight illumina
tion of the entire floor area and are desirable when practicable.
When rooms are illuminated through side windows it is often diffi
cult or impossible satisfactorily to light all parts of the floor space,
furnishing adequate illumination to the workers without subjecting
some of them to objectionable glare. In some cases the use of re
fracting or diffusing glass which redirects the rays of light so as
to improve the distribution of daylight in the room, especially in
the part of the room remote from the windows, is desirable.
If only one side wall contains windows, the width of the room
perpendicular to this wall should be less than twice the height of the
top of the windows above the floor; if windows are in two parallel
side walls, the width of the room between these walls should not exceed
six times this window height. A monitor gives best results when its
width is about half the width of the building and the height of the
windows in the monitor is one-half of the monitor width. The
height of the windows in saw-tooth construction should be at l'east
one-third of the span. In general, single-story industrial buildings
should have a window area of at least 30 per cent of the floor area.
Reflection of daylight from surfaces outside a building has an
important effect upon the lighting of a room. Faces of structures,
walls of courts, and roofs of saw-tooth buildings should be finished
in the lightest practicable colors and so maintained. The possibility
of glare from such surfaces should, however, be considered.
Windows should be equipped with adjustable devices so that the
illumination may be accommodated to changing exterior conditions.
Window shades of light tones should be used, for at night they will
reflect artificial light back into the room; shades transmitting diffuse
ly a large part of the natural' light they receive will generally improve
the daylight illumination. When practicable, shades should be
mounted so as to permit of covering any desired parts of the windows.
Venetian type blinds are effective means to control the distribution of
natural illumination as well as the glare from windows, if properly
finished and adjusted. Any devices for adjustment of natural light
ing should be controlled by some specified individual.
Rapid changes in illumination levels result in dangerous, even
though temporary, inability to see, due to the time required for adap
tation of the eyes. An example of this is when one steps from bright
sunlight into a dimly lighted interior. A passageway adjacent to a
highly illuminated area, therefore, needs relatively high and gradu
ated illumination. Again, where the eye has been afforded the ad
vantages of a high level of illumination throughout the day and
artificial light is turned on to reinforce the failing natural light, a
higher total illumination is ordinarily needed than at night under
artificial1lighting alone.

IN D U STRIAL L IG H T IN G CODE

Maintaining the Level of Illumination
The proper and adequate maintenance of equipment for both
natural and artificial lighting is essential. Systems which are ade
quate when first installed will soon deteriorate unless properly main
tained. The factory owner should establish a regular definite system
of maintenance so as to insure that sky windows, side windows, lamps,
and accessories are at all times kept clean, in proper adjustment, and
in good repair. Means should be provided for easy access to all light
ing units by the employee in charge of their maintenance. Walls and
ceilings should be repainted, preferably in light tones, at regular
intervals, particularly where, as in indirect systems of lighting, a
large part of the illumination comes from the ceiling. It should be
kept in mind that the illumination requirements given in the tables
apply to the lighting equipment under adverse operating conditions,
not simply new and clean as when first installed.
Figures 6 and 7 show the very considerable loss in illumination
which results from the collection of dirt on lamps and lighting fix
tures. To insure that a given level of illumination will be maintained
even where conditions are favorable, it is necessary to design the
system to give initially at least 25 per cent more light than the
required minimum. In locations where the dirt will collect rapidly
and where adequate maintenance is not provided the initial value
should be at least 50 per cent above the minimum requirement, and
it is evident from a study of the charts that even this allowance may
prove insufficient.
Especially in connection with the maintenance of lighting systems
attention is called to the desirability of having available in the fac
tory an instrument with which the foot-candles of illumination
received at any point can be measured. One instrument, the footcandle meter (fig. 8), while not designed for precise measurements,
has a wide field of usefulness because with a little practice determina
tions are easily made with it and are accurate enough for most prac
tical purposes. The foot-candle meter is small, light in weight, and
entirely self-contained. Illumination is read directly from the scale
without computation or manipulation. In one large establishment
where the superintendent uses a foot-candle meter systematically
as a check on his maintenance department, readings of illumination
are taken at regular intervals at fixed stations throughout the plant.
These readings are recorded in such a way that the successive read
ings are readily comparable. When any inconsistency appears in
the records an investigation is made and the remedy applied. The
illumination in that establishment is never allowed to fall below
six foot-candles without immediate correction. By measuring light
actually delivered to the work the foot-candle meter automatically
reveals the combined effect of all possible causes of depreciation.
Ignorance of the magnitude of depreciation has often been the cause
of inadequate maintenance. Soap and water cost less than electrical
energy.
Avoidance of Glare
It is not a particularly difficult problem to supply a factory or
office with the amount of light specified in Table 1, and reflectors

IN D U STRIAL L IG H T IN G CODE

are available which provide these levels economically. There are
many installations, however, where poor conditions for vision exist
in spite of an adequate foot-candle level. This is usually because
precautions were not taken to provide illumination without glare.
Glare may be defined as any brightness within the field of vision
of such a character as to cause discomfort, annoyance, interference
with vision, or eye fatigue. Always a hindrance to vision, it often,
like smoke from a chimney, represents a positive waste of energy
as well. It is one of the most common and serious faults of lighting
installations; the code properly requires the shading of lamps in
industrial plants to guard against glare.
Glare is objectionable because (1) when continued it tends to
injure the eye and to disturb the nervous system; (2) it causes
discomfort and fatigue and thus reduces the efficiency ox the worker;
and (3) it interferes with clear vision, and thus reduces the efficiency
and in many cases increases the risk of accident or injury to the
worker. From both a humanitarian and a business viewpoint the
owner or operator of a factory should be interested in avoiding glare,
whether caused by daylight or by artificial light.
There has been considerable call for a simple instrument for meas
uring glare. If such were available a forward step would be taken
in educating users of light through quantitative comparisons. How
ever, there are so many factors entering into the situation that it
has not been found practical to develop any instrument which will
properly evaluate them all, and such glare data as can be assigned
to a particular light source must be based upon the impression which
it creates upon the eye itself. The eye has the quality of estimating,
with a fair agreement among different observers, which of two light
sources is the more glaring, taking into account both brightness and
oandlepower when the two sources are located side by side and viewed
ugainst the same background. This quality of the eye has been used
as the basis of a relatively simple system of glare rating.
I f a series of comparison standards is supplied, using respectively
10,15, and 25 watt lamps and also larger sizes, each placed in a 6-inch
frosted ball globe, then a light source can be judged as to com
parative glare by placing these standard globes bieside it one by one
and finding which one appears to be equally glaring. For example,
it might be found that a 16-inch semi-indirect lighting unit contain
ing a 300-watt lamp appears to the eye just about equal from the
glare standpoint to a 50-watt lamp in the 6-inch frosted ball globe.
The 300-watt unit would then be classified arbitrarily as Grade E.
(See Table 2.)
T

Grade

A____________
B____________
C____________
D------------------E____________
F------------------G------------------H____________
I_____________
J____________
K____________

able

2
S tand ard

10-w. tung. fila. lamp in 6" frosted ball globe.
15-w. tung. fila. lamp in 6" frosted ball globe.
25-w. tung. fila. lamp in 6" frosted ball globe.
40-w. tung. fila. lamp in 6" frosted ball globe.
50-w. tung. fila. lamp in 6" frosted ball globe.
60-w. tung. fila. lamp in 6" frosted ball globe.
100-w. tung. fila. lamp in 6" frosted ball globe.
150-w. tung. fila. lamp in 6" frosted ball globe.
300-w. frosted lamp.
500-w. frosted lamp.
1,000-w. frosted lamp.

IN D U ST R IA L L IG H T IN G CODE

The above classification is identical with that given in the I. E. S.
Residential Lighting Equipment Specification. It will be observed
that Grade K is representative of light sources which are extremely
bright and glaring whereas Grade A (a 10-watt lamp in a 6-inch
frosted ball) can be placed almost anywhere in the field of view
without causing discomfort.
Where lamps are located at considerable heights above the eye level
relatively bright light sources can be tolerated, and this is particu
larly true in locations such as out of doors at night where little close
discrimination of detail is required of the eye. On the other hand,
where light sources are hung low and are constantly in the field 01
view of a worker seated at a table or work bench, then the light
source should be of Grade A or B.—i. e., very soft and free from
glare. Again, the effect of glare is cumulative; therefore in a long
room where a considerable number of light sources are in one’s field
of vision it is necessary to have better diffused sources than in a room
of limited area where only one or two units are visible to a man
seated at his desk.
T able 3 . —

Grades of light source glare which should not J)e exceeded for good
conditions of vision
Space or work to be lighted1

Offices and
Height of light source above floor in feet Roadways and
Ordinary man drafting work
ufacturing
yard thorough Storage spaces
and certain
operations
fares
manufacturing
operations *
6.5 or less___________________________
6.5 to 7.5..................................................
7.5 to 9..........................................................
9 to 11......................................................
11 to 13.................................. ..................
13 to 16.....................................................
16 to 20.....................................................
20 and u p .......................... .....................

F
G

H
H
I
J

D
D
E
G
G
H
I
J

C
C
D
E
G
H
I
J

A
A
C
D
E
F
G
H

i Where backgrounds are very dark in tone, a light source 1 grade softer than above is recommended for
interiors.
* Those operations in which workers are seated facing in one direction for long periods of time.

For convenience a number of more common light sources have
been rated for glare in accordance with the classification given in
Table 2. The grades assigned to them are shown in Table 4.
T

able

4 . —Specific

classification of common light sources from the standpoint of
glare, as derived from Table 2
Grade

Natural light sources (as seen through windows):
Sun...................................................................
Bright southern sky........................................
Dull or northern sky_.....................................
Sun shining on prism glass...............................
Mercury vapor tubes............................................. .
Carbon incandescent lamps:
16 candlepower................................................ .
32 candlepower................................................ .
6 8 7 9 3 ° — 3 1 -------- 3

K
G
C
J
G
F
G

IN D U ST R IA L L IG H T IN G CODE

12
T a b le 4

.—Specific classification of common light sources from the standpoint of
glare, as derived from Table
Continued
Watts

Tungsten filament lamps:
Bare lamps..... .......................................
Frosted lamps or frosted globes1.........
8-inch opal globes______________ - ___
12-inch opal globes_____ ______ ______
16-inch opal globes__________________
Flat reflectors—filament position visi
ble.......................................................
Dome reflectors—steel or dense glass:
Filament position visible from
working position.........................
Filament position not visible..........
Pome reflectors—white bowl lamps.
Bowl reflectors—steel or dense glass:
Filament position visible................
Filament position not visible_____
Totally indirect lighting i________
Semi-indirect bow l1_____________

100

150 to 200

300

500 to
1,000

Grade
G

Orade

Grade
1
G
F
E

Grade

Grade
J
I

Grade

H
G
F

I
H

D
c

F
E

J-K

G
B

H
B

I
D

J
D
F

J
E
G

G
G

G
C

H
C

J
E
B-C
C-D

J
G
C
C-E

B
B -D

K
K

D-G

1 Where a range is given, the best grade—that is the lowest—applies to bowls that are of dense glass, and
the poorest to bowls which have a decidedly bright spot in the center.

Factors Affecting Glare
In order that the various factors affecting glare may be better
understood, the principal causes are outlined below:
1. Brightness of Source.—The light source may be too bright; that is,
it may have too high a candlepower per square inch of area.
A glance at the sun proves that an extremely bright light source within
the field of vision is capable of producing acute discomfort. Light sources
of far lower brightness than the sun, such, for example, as the filament of
an incandescent electric lamp or the incandescent mantle of a gas lamp,
may also cause discomfort, although the annoying effect is usually not quite
so marked.

2. Total Volume of Light.—The light source may be too powerful for
comfort; that is, it may have too great a total candlepower in the
direction of the eye.
Too frequently glare is assumed to be entirely a question of the bright
ness of the light source; of equal importance is the question of its total
candlepower. Experience has shown that a 500-watt lamp in a 10-inch opal
globe, or a mercury-vapor lamp of an equivalent light output, hung 7 or 8
feet above the floor and a similar distance in front of the observer will
prove quite as glaring as the exposed filament of a 50-watt incandescent
lamp in the same location. The brightness of the opal globe unit is only
a few times that of a candle flame, but its total candlepower and con
sequently the quantity of light which reaches the eye is altogether too
great, so that its effect is worse than that of the bare filament of lower
candlepower, although the latter may have a brightness as high as 3,000
candles per square inch. An unshaded window often causes glare, due, of
course, to the large volume of light rather than to the high brightness of
the sky.

3. Location in the Field of View.—A given light source may be located
at too short a distance from the eye or it may lie too near the center
of the field of vision for comfort; that is, within too small an angle
from the ordinary line of sight.

F i g u r e 1.— C otton -m ill ligh tin g using 200-watt w h ite b o w l lam ps in R . L . M . Standard

dom e reflectors.

T h e average illu m in ation is 8 foot-candles

F i g u r e 2.— A n office ligh ted b y 200-w a tt lam ps in sem idirect units.

is 12 foot-candles

A vera ge illu m in ation

F ig u r e 3.— L ig h tin g a drafting room b y 500-watt lam ps in sem idirect units.
illum ination is 30 foot-candles

T h e average

F i g u r e 4.—Illu m in ation o f tim b e r d o c k b y units suspended from catenary con stru ction

to a v o id o bstru ctin g poles

F i g u r e 5 .— Saw -tooth roof con stru ction , w ith glass facing n orth sky, u sually results in w ell-

diffused dayligh t illu m in ation

Lamps Replaced with
New Lamps of Proper Voltage

Lamps and Reflectors
Cleaned
Interior
Repainted

Illumination
as Found

F i g u r e 6 .— R esults of a test on a carelessly m aintain ed lighting

system , sh ow in g h o w each factor co n trib u te d t o th e p o o r result.
Illustrates th e im p ortan ce o f using lam ps o f the p rop er voltage,
cleaning equ ip m en t system atically , and repaintin g interior at
reasonable intervals

MAINTENANCE

RECORD

JA M FE B MAR A P R MAY
1 IS I 19 i iS i *5 / /5

12 12 12. w
f t ! s

//f

IIS i/s#5 /l5

75 75

7.0

} g o f 1 8 s f 75 7< to 601 7} *
? r i f fr ? r /.C I f t 7.^ 10
t t
&
? I f 7.r >r 7 f

> f5 f * ? *
7.f I f 7 .f 7* 7o
} SV Z f K 7*' 7c ?0 2o 7° 7P ?o 7.0
&
» t S
iff f 9 s *

I t 7 f 75- 75 7o 70

Ih tiu rtu f.
St&uairtM
d

*> 20 70 7.0
3 * f J 75 7 f V 75 IS 7.0
z
2. 2. ■4. 2- 1. * /)
2. 2
2
2. / f Z
/.5

J U N J U L AUG SEP OCT NO V DEC
/ /*■ /•
/ IS / is /
/ IS / '5

Ho
70
f

7o
7o

00 jio
lo 10 70

f 5- 7-5
7o 7.o ?o
7* 7o 70

7o 7»
7o 7o 70 7o
r

;.*■ U' OS
f 5
io To 7o 7-o

f.S

■2. 2

/S X.

JU__ f

F ig u r e 7.— L ig h tin g m aintenance record

8.— A su rvey of actual ligh tin g co n d itio n s can re a d ily be m ade w ith the footcandle m eter. T h is instru m en t is v e r y useful in “ ch eck in g u p ” a ligh ting system to
see th at it is bein g p ro p e rly m ain tain ed

F ig u r e

9a and 9b.— W h en ever local ligh ting is used it should be su p p lem en ted b y som e
general illu m in ation . N o te the absence o f glare and contrast b etw een ligh t and dark
areas in F igure 9b as com pared w ith Figure 9a, w here there is n o general illu m in ation .
I n Figure 9b, although a local lam p is su p p lied for each m achine and ben ch , the in d i
v id u a l sources of ligh t are scarcely apparent, because of the general illum ination

F ig u r e s

10b

F i g u r e s 10a and 10b.— T h e u p p e r figure illustrates a strictly loca l ligh ting system .

T h e low er figure illustrates the sam e loca tion u n d er general illu m in ation . O bserve the
harsh shadow s and glaring ligh t sources w ith local ligh ting, and the absence o f such
sh ad ow s and glare u n d er general ligh tin g

F ig u r e 11.— A textile operation (qu illin g) illu m in ated b y
lam ps

m eans o f m e rcu ry -va p o r

F i g u r e 12.— A n exam ple of w ell-d istrib u ted general illum ination a pp lied to a m odern

m achine sh op. H ere 300-watt lam ps in glassteel diffusers are used on 12-foot centers,
15 feet a b ove the floor. T h e illu m in ation level is 12 foot-candles th roughout. T h e
diffusing equ ipm en t and the high m ou n tin g co m b in e to elim inate glare and produce
soft shadow s

F igure 13.—A press department illuminated with mercury-vapor lamps

F ig u r e

14.— A factory office ligh ted b y 200-watt lam ps in glassteel
diffusers. T h e average illu m in ation is 12 foot-candles

IND U STRIAL LIG H T IN G CODE

The 500-watt opal globe unit discussed in the previous illustration would
seldom cause discomfort if placed, say, 80 feet away from the observer,
for at this distance the total quantity of light entering the eye would be
only one one-hundredth of that received at 8 feet. Again, the same light
source would probably be found quite unobjectionable at a distance of 8
feet from the eye, provided this distance were obtained by locating the
lamp 4 feet ahead of the observer and 7 feet above the eye level; in this
case the lamp would scarcely be within the ordinary field of view.
The natural position of the eye during intervals of rest from any kind
of work is generally in the horizontal direction, and it is desirable that
during such periods the worker should be freed from the annoyance caused
by glare. Glare is the more objectionable the more nearly the light
source approaches the direct line of sight. While at work the eye is usu
ally directed either horizontally or at an angle below the horizontal. Glaring
objects at or below the horizontal should especially be prohibited. The
best way to remove light sources out of the direct line of vision is to locate
them well up toward the ceiling. Local lamps—that is, lamps placed close
to the work—if used must be particularly well screened.

4. Contrast with Background.—The contrast may be too great be
tween the light source and its darker surroundings.
It is a common experience that a lamp viewed against a dark wall is far
more trying to the eyes than when its surroundings appear relatively light.
In order to provide a light background (usually ceiling or side walls) which
will minimize contrasts, the surfaces should be painted a light color and the
system of illumination employed should be such as to direct some light upon
the background. In many cases the ceiling appears almost black under
artificial light simply because no light reaches it. With daylight, on the
other hand, the walls of a room are often so well illuminated that they
appear brighter than the work itself and this also, is a condition which is
not conducive to good vision. In general, a light tone for ceilings and hisrh
side walls and a paint of medium reflecting power for the lower side walls
will ordinarily be found most satisfactory under both artificial and natural
lighting.
Where strictly local lighting systems are employed—that is, where
individual lamps are supplied for all benches and machines—and no
overhead lighting is added, the resulting contrasts in illumination will
usually be found so harsh as to be objectionable even though the lamps
themselves are well shielded. The eyes of the workman looking up from
his brightly-lighted machine or bench are not adapted for vision at low
illuminations; hence, if adjacent objects and aisles are only dimly lighted
he will be compelled either to grope about losing time and risking accident,
or to wait until his eyes have become adapted to the low illumination.
Glancing back at his work, he again loses time while his eyes adjust
themselves to the increased amount of light which reaches them. If long
continued, this condition leads to fatigue, as well as to interference with
vision, and to accidents. In other words, where local lamps are employed,
there should also be a system of overhead lighting which will provide a
sufficient illumination of all surrounding areas to avoid such undesirable
contrasts.

5. Time of Exposure.—The time of exposure may be too great; that
is. the eye may be subjected to the strain caused by a light source
of given strength within the field of vision for too long a time.
Where an operator is seated and his field of vision is fixed for several
hours at a time, light sources of lower brightness and lower candlepower
are required than where the operator stands at his work and shifts his
position and direction of view from time to time. In the first case the
image of the light source is focused on one part of the retina for consider
able periods of time and is obviously more likely to cause discomfort and
eyestrain than when present for short periods only. Those who are forced
to work all day at desks facing the windows are particularly likely to*
suffer from this form of glare.

IN D U ST R IA L L IG H T IN G CODE

Glare by Reflection
Another way in which glare is produced is by the reflection of light
from polished surfaces in the field of vision. The difficulty experi
enced in protecting the eyes from this kind of glare is sometimes very
great. The brightness of the image on the working surface is, of
course, proportional to the brightness of the light source above it,
and hence one way in which to minimize this effect is to diffuse the
downward light; that is, to use a bowl-frosted or bowl-enameled
lamp, or an inclosing fixture, or to employ semi-indirect or totally
indirect lighting fixtures. In some cases the light source can be so
located that its reflection is directed away from, rather than toward,
the eyes of the workers. The avoidance of highly polished surfaces
in the line of vision is another good way to minimize reflected glare.
There are some instances, on the other hand, where sharp shadows
and specular reflection from the materials worked upon actually
assist vision. For example, in sewing on dark, goods the thread is
much more easily distinguished when illumination is secured from
a concentrated lisrht source, such as a brilliant lamp filament, which
casts sharp shadows and gives rise to a distinct glint from each
thread. However, in these cases the light source must be particularly
well shielded from the eyes of the worker.
Importance of Adequate Electrical Wiring
In specifying electrical wiring for a new building, or the revision
of old wiring, it is important to observe the following points:
1. The National Electrical Code regulations are intended to insure
protection from fire hazard, but do not necessarily provide a wire
size sufficient to permit of the most efficient use of lamps and equip
ment, nor do they make provision for future increases of illumina
tion. To take them as a criterion of adequate capacity of a wiring
system, therefore, in the interests of low first cost, is not good
economy in the long run.
2. Wiring should provide for economical distribution of electrical
energy.
Electrical wiring of inadequate size introduces a source of energy
loss between the meter and the outlet, and at the same time causes a
reduction in the voltage at the lamp socket, so that lamps (unless
specially ordered for lower voltage) are operated at a voltage below
that for which they were designed. Operation of lamps at reduced
voltage means that the efficiency of light generation is lower, and
the overall cost of light is higher, than when they are operated at
rated voltage.
When wiring is inadequate, as more lamus are turned on, the
voltage at each socket decreases. Thus as daylight fails and more
artificial light sources are required the illumination secured from
each lamn decreases, producing an annoying variation in illumina
tion at different times and places.
3. Wiring should be of sufficient capacity to provide for future
requirements, as the trend of lighting intensities is ever upward.
Recommended lighting practice and the appreciation on the part
of factory owners and ihanagers for the value of good lighting have

IN D U STRIAL L IG H T IN G CODE

a distinct forward trend, and an installation considered up-to-date
when made may be found quite inadequate at a later date. The
cost of rewiring finished buildings is many times greater than the
additional cost of providing capacity for future requirements in
the original installation.
Specification of Adequate Wiring
The following paragraphs are abstracted from a specification pre
pared by the National Electric Light Association to express the
quantitative requirements which good illumination practice imposes
upon the wiring.
This specification is in conformity with the regulations of the Na
tional Electric Code, as regards current-carrying capacity and in
addition makes reasonable provision for economical distribution of
energy and the probable lighting requirements of the near future.
In this specification, it is assumed that each branch circuit will
be fused for 15 amperes.
Branch circuits.—A single branch circuit should not be required
to supply the general lighting for a work space greater than 400
square feet or a bay approximately 20 feet by 20 feet, nor should
it be required to supply the overhead lighting for more than 800
square feet of hall or passageway or other nonproductive area.
Based on the wattage of outlets specified on the plans, branch cir
cuits should be so arranged that the initial load on a single circuit
will not exceed 1,000 watts, except in the case of a single lamp of
larger size.
The smallest size wire that should be used is No. 12 gage, and
for runs from a panel board to the first outlet of from 50 feet to
100 feet, No. 10 gage wire is the smallest that should be used, with
No. 12 between outlets.
Runs exceeding 100 feet from panel board to the first outlet should
be avoided by addition or relocation of panel boards. Where such
runs can not be avoided, the lamp load should be limited to 600 watts
for each branch circuit.
Convenience outlets should be placed on a circuit separate from
that supplying general lighting. Such outlets should be of the duplex
type, with not more than six grouped on one circuit. For runs from
the panel board to first outlet under 100 feet, wire not smaller than
No. 12 gage should be used and No. 10 gage where the runs must be
longer.
Panel boards.—Panel boards should contain at least one spare
circuit position for each five active circuits or fraction thereof. It
is generally desirable to supply each circuit position with a switch.
There should be provided at least one panel board on each floor
of the building. Wherever possible, panel boards should be so
located that branch-circuit runs exceeding 100 feet to the first outlet
can be avoided.
Feeders.—The current-carrying capacity of a feeder should be
sufficient to supply 7.5 amperes (115 volts) to every 15-ampere
circuit position provided for on the panel board or boards which it
feeds.
The feeders should be of such size that the voltage drop from the
service switch to the panel board will not exceed iy2 per cent with a

IN D U ST R IA L L IG H T IN G CODE

load of 7.5 amperes (115 volts) on every branch circuit provided
for.
Conduits for inclosing feeders should be of sufficient size to permit
replacing the original feeders with wires two standard gage sizes
greater in capacity.
Locating Switches
The switches which turn on and off the light in entrances and halls
of buildings should be located near the point of entrance. Likewise
a switch which controls at least one circuit of lamps in a room should
be located near each principal point of entrance to that room.
In locating switches or control devices in factory and mill aisles
care should be exercised to arrange them systematically; that is, on
columns situated on the same side of the aisle and on the same rela
tive side of each column. This plan materially simplifies the finding
of switches or control devices by those responsible for turning on and
off the light.
For control purposes groups of lamps may constitute a square,
a row parallel to the windows, or a row perpendicular to the win
dows. The arrangement on a square has the most to recommend
it, as any worker within the area gets the benefit of several near-by
lighting units. A row parallel to the windows is occasionally desir
able, since when daylight fails those workers farthest from the
windows can have one or two rows lighted to supplement the natural
light. If two rows are used, the merits of the square arrangement
are to a great extent retained. Control of rows perpendicular to
the windows is usually to be avoided, as grouping in a square can
almost always be applied to better advantage.

Part 3.— Suggested Minimum Regulation to be Estab
lished by State Authorities
Purpose
The purpose of this code is to make reasonable provisions for the
safety of workers by requiring such illumination as may be neces
sary to conserve vision and to facilitate the utilization of eyesight
for the prevention of accident.
Exceptions
In cases of practical difficulty or unnecessary hardship the enforc
ing authority may grant exceptions from the literal requirements
of this code or permit the use of other methods but only when it
is clearly evident that safety is thereby reasonably assured. There
are occasional operations which need to be performed practically
without light, such as photographic and photometric processes in
dark rooms. Again, there are some operations which are best ob
served by their own light, as in certain parts of the process of
working with glass. In all cases in which work must be performed
under very low illumination, special 'precaution should be taken to
safeguard the workers from accident.

IN D U ST R IA L L IG H T IN G CODE

Scope
This code applies to all factories, mills, offices, storage buildings,
yards, power houses, and other industrial and mercantile establish
ments and work places.
Rules
General Requirement.—Illumination, daylight or artificial light, in
accordance with the following rules, shall be supplied for—
1. Traversed spaces such as hallways, roadways, etc., during work
ing hours, and
2. Work when attended by operators.
N o t e : It should be recognized that the foot-candles specified represent mini
mum limits, and that tolerance for depreciation must be made in the design
of the installation. The values are established to meet the needs of safety and
are not to be interpreted as providing for effective and economical operation
of processes. Higher levels representing good lighting practice are recommen
ded in Table 1, and general suggestions for design will be found on pages 14
to 16. Information on the measurement of illumination values will be found
on page 14.

Rule 1. Illumination Required.—The illumination maintained shall
be not less than given in Table 5.
T able 5

1. Minimum foot-candles on traversed spaces
Foot-candles

Roadways; yard thoroughfares-------------------------------------------------------- 0.02
Storage spaces, aisles and passageways in workrooms, excepting exits and
passages leading thereto_________________________________________ .5
Spaces, such as haUways, stairways, exits, and passages leading thereto___ 75
Spaces, such as stairways, locker rooms, wash rooms, toilet rooms, and
passageways where there are exposed moving machines, hot pipes, or
live electrical parts, also elevator cars, and landings________________ 1
2. Minimum foot-candles at the work
Where discrimination of detail is not essential------------------------------------ 0.5
Work, such as handling material of a coarse nature; grinding clay
products; rough sorting; coal and ash handling; foundry charging.
Where slight discrimination of detail is essential--------------------------------- 1
Work, such as rough machining, rough assembling; rough bench
work; rough forging; grain milling.
Where moderate discrimination of detail is essential___________________ 2
Work, such as machining; assembly work; bench work; fine core
making in foundries.
Where close discrimination of detail is essential_______________________4
Work, such as fine lathe work, pattern making; tool making; weav
ing or sewing light-colored silk or woolen textiles; office work;
accounting; typewriting.
Where discrimination of minute detail is essential_____________________8
Work, such as drafting; weaving or sewing dark-colored material;
very fine inspection or inspection of very dark goods.

Rule 2. Avoidance of Glare: Diffusion and Distribution of Light.—
Lighting, whether natural or artificial, shall be such as to avoid
glare, objectionable shadows, and extreme contrasts, and to provide a
good distribution of light; in artificial lighting systems, lamps shall
be so installed in regard to height, location, spacing, and reflectors,
shades, or other suitable accessories as to accomplish these objects.

IN D U STRIAL L IG H T IN G CODE

Bare light sources, such as exposed lamp filaments, located within
the ordinary field of the worker’s vision, are presumptive evidence of
glare.
For a specification of definite requirements under this rule refer
ence should be had to Tables 2, 4, and 6.
Rule 3. Exit and Emergency Lighting.—The lighting to be provided
under rule 1 in all important stairways and all exits of work places
and in the passageways appurtenant thereto shall be supplied so as
not to be subject to failure because of the failure of the room or
work-space lighting from internal causes. In the case of artificial
illumination the service should be preferably from an independent
connection or connections extending back to the main service entrance
for the building. In cases of unusual danger which may exist on
account of the type of building or nature of the work, crowded
conditions, or lack of suitable exit space, an independent service shall
be insured by connecting to a separate source of supply without or
within the building. During the hours of occupancy, when daylight
of the value given in rule 1 is lacking, this separate source of supply
shall be connected so as to function continually or to come on auto
matically upon failure of the regular lighting service.
Notes on Rules
Notes on Rule 1. Illumination Required.—In Table 5 the lower values,
up to 1 foot-candle, are required principally to enable employees to
see well enough to avoid accident, while the higher values have the
additional purpose of preventing eyestrain and so conserving vision.
The values have been assigned on the basis of engineering experience
and assume the average conditions found in practice. There are
no sharp lines of demarcation. A specified process is carried on in
different establishments with varying degrees of fineness. Where
especially close attention to the fine detail is required, it is obvious
that more illumination is needed than where the process is made
more automatic or operated on a coarser scale. Where such special
conditions exist the next higher or lower classification may be found
the reasonable requirement.
Notes on Rule 2. Avoidance of Glare.—It is assumed that in inter
preting the enforcing of the regulation against glare the enforcing
officer will not insist upon what he might consider as pleasing or
desirable practice in any given case. It is the intention of the rule
merely to prevent conditions which are prejudicial to the physical
welfare of the worker.
Table 6 shows the harshest grade of light source that may be
used under any particular set of conditions. It is based on the
system of glare rating described on pages 9 to 12, where an explana
tion of the symbols used will be found.

IN D U ST R IA L L IG H T IN G CODE
T a b l e 6 .— Limiting

grades of light sources permissible for various conditions1

[The grades given in this table are limiting values; from 1to 2 grades softer are recommended, see Table 3]
Space or work to be lighted1

Height of light source above
floor in feet

Roadways
and yard
thorough
fares

Storage
spaces

Ordinary manufactur
ing operations *

Short
rooms3
6.5 or less___________________
6.5 to 7.5....................................
7.5 to 9......................................
9 to 11........................................
11 to 13......................................
13 to 16......................................
16 to 20......................................
20 and up..................................

H
I
J
J
K
K

F
Q
H
I
J
J
K
K

D
F
H
I
J
J
K
K

Long
rooms3
D
F
G
H
I
I
J
K

Offices a n d drafting
work an d certain
manufacturing opera
tions
Short
rooms8
0
E
G
H
I
I
J
K

Long
rooms4
0
E
F
G
H
H
I
J

1 Where backgrounds are very dark in tone a light source of one grade softer than specified may be re
quired in the case of all indoor classifications.
2 For the present the limits set in this table can not be rigidly applied to portable lamps used for temporary
work, such as setting up machines, repairing automobiles, etc.
* A “ long” room is considered to be one in which the total length in feet is more than twice the height of
the lamps above the floor; one having a length less than twice the height of the lamps above the floor is
classified as “ short.”
* Those operations in which workers are seated facing in one direction for long periods of time. See also
note 3.

Notes on Rule 3. Exit and Emergency Lighting.—The employer is to
be held responsible for the proper lighting of passageways, stair
ways, and exits, in so far as his premises are concerned, which
means such parts of buildings, floors, or rooms as are controlled by
the employer, including entrances thereto, but excluding hallways,
passageways, and stairways giving access to other floors, or to spaces
on the same floor, and used m common by the tenants of the build
ing. These latter should be lighted by the building owner.
Exit and emergency lighting are to be understood as those artificial
illuminants which are necessary only to make clear to the occupants
or employees the places of exit, or to enable them to pass to and
along safe exits with reasonable speed and assurance of footing.
Such lighting is not assumed as being necessarily sufficient for the
proper performance of regular working operations.
The circuits for exit electric lamps should be' separate branch
circuits, including no other lamps, and containing no receptacles or
convenience outlets for the attachment of portable or other devices.
Being thus separately fused, trouble on other circuits which causes
the blowing of fuses will be less likely to affect them.
The main service entrance may be interpreted to mean the entrance
point (meter or distributing panel) of lighting feeders for the
building, floor, loft, or particular space in question. In gas lighting
it may be considered to be the main gas feeder for the building, or
the main gas riser for the floor or loft in question. Where several
factory spaces are grouped in the same building, each with its own
exit or exits, the emergency electric circuits for any one space are
not required to run to the main building panel board or main
switch nor are the emergency gas pipes expected to extend to the
main gas meter nor to the building feeder from the street main,
except as explained below.

INDUSTRIAL. L IG H T IN G CODE

Under specially dangerous conditions, where in the opinion of the
recognized authorities the failure of the main and entire regular
lighting supply would leave the employees without assured means
of seeing tne outgoing passageways, the exit and emergency lamps
should be fed from an entirely separate source of energy, such as
a storage battery, or, in case the regular lighting system is electric,
from gas or other reasonably dependable illuminant. Service from
an independent street main, where available, is regarded as a sepa
rate source of supply; or a separate service from an independent
transformer fed from the same primary wires will usually be con
sidered sufficient. Factories supplied by an isolated plant should
feed exit circuits from an independent source or utilize a separate
generating unit driven by a separate prime mover. Such an inde
pendent supply as discussed in this paragraph is not considered
necessary for typical conditions, but only where the large number
of persons concerned or other special condition calls for special
precautions. Such a condition may be recognized by the manage
ment, but if doubt exists a decision should be asked from the inspec
tion department having jurisdiction.
As indicated in the general requirements of this regulation, the
exit and emergency lamps should be lighted whenever artificial
lighting is required in the work spaces.
It is the obvious intent of rule 3 to insure reduction of accident
hazard; and inasmuch as this end is as beneficial to the industrial
operator or owner as to the State, the detailed interpretations of
this order, for the various types and situations of working spaces,
can only be reached through mutual cooperation of the owner and
the State authorities.

Subject Index
O ccidents:
Page
Cost o f industrial______________
2 -3
Insurance costs________________
3
Loss o f time due to____________
2
Reduction o f____________________
2
Advantages o f good illum ination----2 ,1 7
Background.
Contrast with light
source_____________________ 13,17—18, 19
Bare lamps. Source o f glare____ 9 -1 0 ,1 2
Branch circuits. Specification fo r __
15
Brightness o f light source_________ 12 ,18
Classification o f light sources from
standpoint o f glare________ 1 0 -1 2 ,1 8 -1 9
Cleaning reflectors and lamps____ 3, 9 ,1 7
Code o f lighting factories, mills and
other w orkplaces:
JJotes on revision o f_________ y, 1 ,1 6
P u rp ose-------------------------------------1 ,1 6
Rules------------------------------------------ 17-18
17
Scope----------------------------------------Sectional committee personnel,
v , vi
Contrast with background_________
13 ,19
14—16
Control______________________________
Cost o f light. Economics o f_______
3-4
Daylight.
{See Natural lighting.)
Depreciation due to dirt___________
9 ,1 7
Diffusion and distribution o f lig h t :
Conditions applicable to_ 9 -1 0 ,1 2 ,1 4
Rules covering__________________17-18
Economy o f good illum ination:
Econom ics o f___________________ 3-4, 9
Investment and operating costs3
Exit and emergency lighting________
18
Feeder carrying capacity___________ 15-16
F oo t-ca n ile :
Definition o f____________________
4
Meter___________________________
9
Values recommended___________
5 -7
Values required________________
17
Fuses fo r exit and emergency light
ing------------------------------------------------19
G lare:
Avoidance o f_____________ 9 -1 0 ,1 7 -1 8
Classification o f light sources
from standpoint o f__________ 10-12
Definition o f____________________
10
F actors affecting—
Brightness o f source_______
12
Contrast with background13
Location in field o f v ie w - 12-13
Time o f exposure__________
13
Volume o f light____________
12
Objectionable features o f_______
10
Reflection of, from polished sur
14
faces__________________________
Illum ination:
Advantages o f good____________
2 ,4
Economics o f good______________
3 -4

Illumination— Continued.
M aintaining proper level_______
Measurement o f________________
Natural_________________________
Recommended levels o f_________
Required levels o f______________
Rules fo r proper_______________

Page
3, 9
4
7 -8
5 -7
17
17
2 -3
Insurance accident costs___________
Lamps. Source o f glare from b a re. 9-10,
12 ,18
Light. Excess of, causing glare- 1 2 ,1 7 -1 8
L ig h tin g :
Avoidance o f glare in____ 9 -1 0 ,1 7 -1 8
7 -8
Natural_________________________
Rules fo r proper_______________
17
Light sou rces:
Brightness of, causing glare___
12
Classification of, from standpoint
o f glare______________________ 10-12
Lim iting grades permissible for
specific locations_____________ 11-12
Lim iting grades permissible for
various locations_____________ 11 ,19
Locating switches and controls____
16
Location o f light sources in field o f
view___________________________ 1 2 -1 3 ,1 9
Losses due to poor illum ination____
2 -3
Maintenance o f lighting system— 3, 9 ,1 7
Measurement o f illum ination_______
4, 9
M onitor construction for natural
lighting-----------------------------------------8
Natural lig h tin g :
Control o f ______________________
7 -8
Maintenance o f ________________
9 ,1 7
17
Minimum requirements fo r____
M onitor construction fo r_______
8
7 -8
Proper design fo r --------------------Range between artificial light
ing and---------------------------------7
W indow dimensions fo r________
7 -8
Painting walls and ceiling__________
13
Panel b o a rd s-----------------------------------15
Production increase due to better
light_______________________________
4
Rating o f light sources from stand
point o f glare------------------- 1 0 -1 2 ,1 8 -1 9
Recommended foot-candle values—
5 -7
Reflected glare----------------------------- 1 3 ,1 7 -1 8
Required foot-candle values________
17
R u le s:
Avoidance o f glare_____________ 17-19
Diffusion and distribution o f
light---------------------------------------- 17-18
E xit and emergency lighting___ 18 ,19
Illum ination required---------------- 17 ,1 8
Saw-tooth roof. Design o f_________
8
Shades fo r windows------------------------8

SU B JE C T IN D EX

State co d e s:
Page
Reasons fo r _____________________
1 ,1 6
Suggested rules________________ 17-18
Switches and controls__________ 1 5 ,1 0 ,1 8
Vision. Effect o f glare on_______1 0 ,1 2 -1 3
Walls, color o f______________________
13
W in d ow s:
Design of, fo r natural lighting__
7 -8
Shading o f__________ __ ___ ___ 8

W ir in g :
Branch circuits------------------------F eed ers_________________________
Importance o f adequate________
Panel b oa rd s----------------------------Specification o f adequate_______
Switch location____ __— _____ _

Page
15
15-16
14
15
15
16

Full text of Code of Lighting: Factories, Mills and Other Work Places : Bulletin of the United States Bureau of Labor Statistics, No. 556

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