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U. S. DEPARTMENT OF LABOR
JAMES J. DAVIS, Secretary

BUREAU OF LABOR STATISTICS
ETHELBERT STEWART, Commissioner

BULLETIN OF THE UNITED STATES'!
BUREAU OF LABOR S T A T IS T IC S / • • * *
SAFETY

CODE

{No. 331

SERIES

CODE OF LIGHTING: FACTORIES
MILLS AND OTHER WORK PLACES




PREPARED UNDER SPONSORSHIP OF

ILLUMINATING ENGINEERING SOCIETY
NEW YORK, N. Y .

AMERICAN STANDARD
Approved December 31, 1921, by
American Engineering Standards Committee

APRIL, 1923

WASHINGTON
GOVERNMENT PRINTING OFFICE
1923




A D D I T I O N A L C O P IE S
OF THIS PUBLICATION M A Y B E PROCURED FROM
TH E SUPERINTENDENT OF DOCUMENTS
GOVERNM ENT PRINTING OFFICE
W A SH IN G T O N , D C .
AT

10 C E N T S P E R C O P Y
PURCHASER AGR EES NOT TO RESELL OR DISTRIBUTE THIS
COPY FOR PR O FIT— PU B. R E S . 5 7 , APPROVED M A Y H , 1922

II

CONTENTS.
Page.

Introduction......................................................................................................................
1, 2
Part I.— Rules................................................................................................................
3
Part II.— Suggestions and general information...................................................... 4-25
Notes on Rule 1.—Illumination required, foot-candles:
Natural lighting................................................................................................
6-8
Maintenance of illumination.......................................................................... 8-11
Locating switches and controls......................................................................
11
Control parallel to windows............................................................................
11
Notes on Rule 2.—Avoidance of glare:
Reasons for avoiding glare..............................................................................
11
Causes of glare.................................................................................................. 13,14
Rating light sources from the glare standpoint.......................................... 14-21
Location in field of view.................................................................................
20
Glare limits for specific locations.................................................................. 20, 21
Glaring reflections............................................................................................
21
Notes on Rule 3.—Exit and emergency lighting.............................................. 21-24
Part I I I .—Advantages of good illumination............................................................ 26-28
Illumination v . Accident Insurance Costs..........................................................
28




in

ILLUMINATING ENGINEERING SOCIETY.
The Illuminating Engineering Society was organized in 1906 to
advance the theory and practice of illuminating engineering and to
disseminate knowledge relating thereto. The society now has about
1,200 members who are interested in the subject of lighting from
various standpoints: Engineering, economic, hygienic, esthetic.
The society has no affiliation with any commercial organization.
Any one 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 6 American Standard” by, the
C
American Engineering Standards Committee. 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:
American Gas Association.
American Institute of Electrical Engineers.
American Society of Mechanical Engineers.
Association of Edison Illuminating Companies.
Illuminating Engineering Society.
International Association of Industrial Accident Boards and Commissions.
National Association of Cotton Manufacturers.
National Electric Light Association.
National Safety Council.
National Workmen’s Compensation Service Bureau.
United States Bureau of Standards.
United States Department of Labor.
United States Public Health Service (Department of Industrial Hygiene).

IV




BULLETIN OF THE

U. S. BUREAU OF LABOR STATISTICS
no . 331

W ASHINGTON

a p r il ,

in

CODE OF LIGHTING: FACTORIES, MILLS, AND OTHER
WORK PLACES.
INTRODUCTION.
The accompanying code of lighting for factories, mills, and other
work places* has been prepared and issued by the Illuminating
1
Engineering Society in order to make available authoritative infor­
mation for legislative bodies, factory boards, public-service commis­
sions, and others who are interested in enactments, rules, and
regulations for better lighting. The code is intended also as a guide
for factory owners and operators in their efforts to improve lighting
conditions in their factories.
Part I contains rules arranged in convenient form for legal enact­
ment or governmental regulations.
Part II contains a discussion of the rules of Part I— that is, the.
legal requirements which must be met where a code is in force— and
also suggestions and general information as to desirable practice in
factory lighting.
Part III takes up the advantages of proper and adequate illumina­
tion, both natural and artificial, and discusses such lighting particu­
larly from the standpoint of economics.
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 the employees, have adopted
factory lighting codes. As a rule these codes stipulate the minimum
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 equipment 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 industrial
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 similar plants which are well 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; o f flickering light;
of sharp shadows; of glare reflected from polished parts of the work. To conserve
the eyesight of the working class is a distinct economic gain to the State, but regardless
of that, humanitarian considerations demand it.
1 Am erican Standard. A pproved D ec. 31, 1921, b y A m erican Engineering Standards Com m ittee.




1

2

CODE OF LIGHTING FOR FACTORIES, MILLS, ETC.

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.

Mr. R. E. Simpson, of the Travelers’ Insurance Co., is authority
for the statement that during the year 1919 there were more than
2,000,000 industrial accidents causing loss of time; of this number
25,000 were fatal. The following extract from an article in the
Travelers’ Standard by Mr. Simpson gives some interesting data on
the relation between lighting and safety:
There is some foundation for assuming that 18 per cent of our industrial accidents
are due to the defects in lighting installations. On that basis the services of 108,000
men for one year are lost annually because the illumination provided is not adequate
for the safety of the workmen. That this condition could exist year after year is all
the more reprehensible because of the fact that the remedy is so easily applied and
has beneficial results in many ways other than the safety involved. Accidents caused
b y carelessness, inattention, or ignorance can be eliminated only b y a long-continued,
painstaking, educational campaign, often involving a change in long-established
habits. Elimination of accidents due to inadequate or improper lighting is sim ply
a matter of purchasing the proper equipment and installing it under competent
directions. In fact, it seems proper to include illumination in the list of mechanical
safeguards, for the reason that the lamps and reflectors provide a guard; illumination
points out the hazards just as effectively as a railing points out the danger of and pro­
vides protection against the hazard of a revolving flywheel.




PART I.— RULES.
N o te .—A tten tion is called to the fact that the requirem ents given in the rules are m inim um specifica­
tions and are n ot to be interpreted as sufficient to insure good lighting. See Part II.—Suggestions and
general inform ation.

General Requirement.— Traversed spaces, during the time of use,
and work in process, shall be supplied with light in accordance with
the following rules:
Rule 1.— Illumination Required.— The illumination maintained
shall be no less than given in the following table:
TABLE I.
MINIMUM FOOT-CANDLES ON TH E SPACE OR A T TH E W O R K .
Roadways; yard thoroughfares.................................................................................
Storage spaces; aisles and passageways in workrooms, excepting exits and
passage leading thereto.....................................................................................
(c) W h e r e d i s c r i m i n a t i o n o f d e t a i l i s n o t e s s e n t i a l ..........................................................
Spaces, such as—Hallways, stairways; exits, and passages leading
thereto; toilet rooms; elevator cars and landings.
Work, such as—Handling material of a coarse nature; grinding clay
products; rough sorting; coal and ash handling; foundry charging.
( d ) W h e r e s l i g h t d i s c r i m i n a t i o n o f d e t a i l i s e s s e n t i a l .......................................................
Spaces, such as— Stairways, passageways, and other locations where
there are exposed moving machines, hot pipes, or live electrical parts.
Work, such as— Rough machining, rough assembling; rough bench work;
rough forging; grain milling.
( e ) W h e r e m o d e r a t e d i s c r i m i n a t i o n o f d e t a i l i s e s s e n t i a l ..................................................
Work, such as—Machining; assembly work; bench work; fine core
making in foundries; cigarette rolling.
( / ) W h e r e c l o s e d i s c r i m i n a t i o n o f d e t a i l i s e s s e n t i a l ......................................................
Work, such as—Fine lathe work, pattern making; tool making; weav­
ing light-colored silk or woolen textiles; office work; accounting; type­
writing.
( g ) W h e r e d i s c r i m i n a t i o n o f m i n u t e d e t a i l i s e s s e n t i a l . ..................................................
Work, such as—Watchmaking; engraving; drafting; sewing darkcolored material.
(a )
(b )

0.02
.25
.5

1

2
3

5

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 re­
flectors, shades, or other suitable accessories, as to accomplish these
objects.
Hare light sources, such as exposed lamp filaments or gas mantles,
located within the ordinary field of the worker’s vision, are pre­
sumptive evidence of glare.
For a specification of definite requirements under this rule, refer­
ence should be had to Tables III, IV , V , and V I in Part II.
Rule 3.— Exit and Emergency Lighting.— The lighting to be pro­
vided under rule 1 in all stairways and exits of factories 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, and preferably from an independent
connection extending back to the main service entrance for the
building. In case oi unusual danger which may exist on account
of type of building, 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.




PART

n.—
SUGGESTIONS AND

GENERAL INFORMATION.

NOTES ON RULE I—ILLUMINATION REQUIRED.

•The illumination values given in Table I are minimum requirements
dictated from the viewpoint of safety. Table II given below is
intended to indicate the order of illumination values that are con­
sidered desirable for different classes of work. Letters in parentheses
following foot-candle values refer to the corresponding subdivisions
of Table I. Persons of advanced years and those with defective eyes
require more light than those having perfect vision. The foot-candles
in good lighting practice are as a rule several times those specified as
minimum requirements. A range of foot-candle values is given in
Table II for each group of operations; in modem practice it will
usually be found desirable to select values in or even beyond the
upper portion of the range.
TABLE n .

APPROXIM ATE FOOT-CANDLES IN GOOD LIGHTING PRACTICE ON THE
SPACE OR AT THE WORK.

to

J

F oot-Candles.

(a)

Roadways and yard thoroughfares.

1 to 2 F oot-Candles.

(b)

Storage spaces: Aisles and passageways in workrooms, excepting exits and passages
leading thereto.
t o
oot andles
(c) and (d)

2

5F

Auditorium s and assembly room s.
Assem bling: Rough.
B oilers , engine room s, and power houses:

-C

.

Boilers, coal, and ash handlings, storagebattery rooms, auxiliary equipment, oil switches, and transformers.
Chemical works, hand furnaces, boiling tanks, stationary driers, stationary or gravity
crystallizing, mechanical furnaces, generators ana stills, mechanical driers,
evaporators, filtration, mechanical crystallizing, bleaching.
Clay products: Grinding, filter presses, kiln rooms, molding, pressing, cleaning, and
trimming.
Elevator , cars and landings: (Freight and passenger).
Forge shops and welding: Rough forging.
F oundries: Charging floor, tumbling, cleaning, pouring and shaking out.
Glass works: Mix and furnace rooms, casting.
H allw ays: Stairways, exits, and passages leading thereto.
Leather manufacturing: Vats, cleaning, tanning, and stretching.
Locker room s.
M eat packing: Slaughtering.
Machine shops: Rough bench and machine work and rough assembling.
M illing a n d grain fo od s: Cleaning, grinding, or rolling.
Packing: Rough.
P ain t shops: Dripping, spraying, firing.
4




CODE OF L IG H T IN G FOR FACTORIES, M IL L S, ETC.

5

Paper manufacturing: Beaters, machine grinding.
Plating.
Receiving and shipping.
Soap manufacturing: Kettle houses, cutting, soap
Steel and iron m ills: Charging and casting floors,

chip and powder.
muck ana heavy rolling, shearing
(rough by gage), picking and cleaning, soaking pits and reheating furnaces.
Storerooms and stock room s: Rough.
Textile m ills: (Cotton) opening and lapping, carding, drawing-frame, roving, dyeing;
(Woolen) carding, picking, washing and combing.
Toilet and wash room s.
Woodworking: Rough sawing

and rough bench work.

5 to 10 F oot-Candles.

(e) and (f)

Assem bling: Medium fine.
Chemical works:. Tanks for cooking, extractors, percolators, nitrators, electrolytic cells.
Clay products: Enameling, coloring, and glazing.
Cloth products: Light goods.
Electric manufacturing: Storage battery, molding of grids, coil and armature winding,

mica working, insulating process.
Switchboards, engines, generators, blowers, com­
pressors.
Forge shops and welding: Fine forging and welding.
Foundries: Fine molding and core making.
Glass works: Grinding, glass blowing machines, cutting, polishing, inspecting.
Glove manufacturing: Light goods: sorting, stitching, trimming, and inspecting.
E a t manufacturing: Dyeing, stiffening, braiding, cleaning and refining, forming,
sizing, pouncing, flanging, finishing and ironing; sewing—light goods.
Ice making: Engine and compressor rooms.
Inspecting: Rough, medium.
Leather manufacturing: Cutting, fleshing, and stuffing, finishing and scarfing.
Leather working: Pressing and winding, grading, matching, cutting, scarfing; sewing—
light goods.
Machine shops: Medium bench and machine work, ordinary automatic machines,
rough grinding, medium buffing, and polishing.
Meat packing: Cleaning, cutting, cooking, grinding, canning, and packing.
M illing and grain food s: Baking, roasting.
Office: Private, general.
Packing: Medium, fine.
Paint shops: Rubbing, ordinary hand painting and finishing, fine hand painting and
finishing.
Paper manufacturing: Calendering, finishing, cutting, and trimming.

Engine rooms and power houses:

Polishing and burnishing.
Printing industries4 Matrixing

and casting, miscellaneous machines, presses; proof­
reading, lithographing, electrotyping.
Rubber manufacturing and products: Calenders, compounding mills, fabric preparation,
stock cutting, tubing machines, solid-tire operations, mechanical goods building,
vulcanizing, bead building, pneumatic tire building and finishing, inner-tube
operation, mechanical goods trimming, treading.
School: Classroom, study room, library.
Sheet-metal works: Miscellaneous machines, bench work; punches, presses, shears,
stamps, welders, spinning.
Shoe manufacturing: Hand turning, miscellaneous bench and machine work; inspect­
ing and sorting raw material, cutting, lasting, and welding—light goods.
Soap manufacturing: Stamping, wrapping, and packing, filling and packing powder.
Steel and iron m ills: Bar sheet and wire products; automatic machines, rod light and
cold rolling, wire drawing, shearing, fine by line.
Storerooms and stock room s: Medium, fine.
Structural steelfabrication.
Textile m ills: (Cotton) spooling,

spinning, drawing in, warping, weaving, quilling,
inspecting, knitting, slashing. (Silk) winding, throwing^ dyeing, quilling, warp­
ing, weaving, and finishing. (Woolen) twisting and dyeing; drawing in, warping;
weaving; knitting machine—light goods.
Woodworking: Sizing, planing, standing, machine and bench work, gluing, veneering
cooperage, finishing.

23

31517°— —Bull.




331---- 2

CODE OF L IG H T IN G FOR FACTORIES, M IL L S , ETC.

6

10

to

20 F oot-Candles

and

A bove .

(g)

Assem bling: Extra fine.
Cloth products: Dark goods.
G lassw orks: Glass cutting (cut glass); inspecting, fine.
Glove manufacturing: dark goods—sorting, stitching, trimming, and inspecting.
Hat manufacturing: Sewing—dark goods.
Inspecting: Fine.
Jewelry and watch manufacturing: Engraving, stone setting, fine repairing.
Leather working: Grading, matching, cutting, scarfing, sewing—dark goods.
Machine shops: Fine bench and machine work, fine automatic machines, fine grinding,

fine buffing and polishing.
Office: Drafting room.
Paint shops: Extra fine

hand painting and finishing (automobile bodies, piano cases,

etc.).
Printing industries: Linotype, monotype, typesetting, imposing stone,'engraving.
Shoe manufacturing: Inspecting and sorting raw material, cutting, stitching-—
dark

goods.
Textile m ills:

Woolens; weaving—dark goods.

In Tables I and II the illumination requirements are specified in
foot-candles. The term “ foot-candle” may be explained by saying
that it represents the illumination on a surface 1 foot distant from
a standard candle; two foot-candles would represent the illumination
supplied by two candles at the same distance, etc. In this illustra­
tion it is assumed, of course, that in each case the surface is perpen­
dicular to the direction of the rays of light falling upon it.
At first sight it might appear from Tables I and I I that there is a
sharp line of demarcation between those operations for which one
foot-candle is specified and those which require two foot-candles, etc.
In reality no such well-defined classification exists and in applying
the tables the inspector will find that in certain cases, because o f the
degree of fineness of the work carried on in a particular plant, one
grade higher or one grade lower than that which first suggests itself
may be a more reasonable requirement.
Again, it should not be overlooked that there are occasional opera­
tions 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 observed by their own fight, as in
certain parts of the process of working with glass. In all cases in
which work must be performed under very low illiunination, special
precaution should be taken to safeguard the workers from accident.
In applying the illumination requirements as given in Tables I
and II the foot-candles specified should not be construed as referring
only to a horizontal plane; the illumination should be measured on
whatever plane the work or operation is carried on, whether it is on a
horizontal, vertical, or intermediate plane. With most artificial
lighting systems the foot-candles measured on a vertical plane are
about one-half the illumination in the same location measured on a
horizontal plane. Attention is also called to the fact that the values
in Table I are minimum values; that is, they apply to measurements
of the lighting system in ordinary operation, not simply when the
lamps and reflectors are new and clean.
Natural lighting.—The foot-candle values given apply to natural
as well as to artificial lighting. In practice it will be found that the
natural illumination on clear days is frequently many times these
figures; in fact, an illumination of a hundred foot-candles can be found
in almost any shop if measurements are taken near the window, and




CODE OF LIGHTING FOR FACTORIES, MILLS, ETC,

F ig . 1.— S aw -tooth roof co n stru ctio n , w ith glass facing th e n o r th sk y , u su a lly results in w e ll
d iffu sed d a yligh t illu m in ation .

Final Intensity

Occasional Maintenance

No Maintenance

Periodic but Inade­
quate Maintenance

F ig . 2.— C hart sh ow in g th e im p o r ta n c e o f p r o m p t renew al o f b u rn ed o u t lam ps
and system atic cleaning of th e lighting e q u ip m e n t. T h ese p articu lar tests
w ere on sem i-indirect a n d in d ire ct ligh tin g system s.




7

8

CODE OF LIGHTING FOR FACTORIES, MILLS, ETC.

very often mechanics find it worth while to avail themselves of this
illumination by walking over to the window whenever extremely
accurate measurements are to be made. In this connection 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. However,
wide extremes in illumination are ordinarily not conducive to best
vision.
Most factory owners 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 periods
when artificial lighting is needed. The saw-tooth sky windows of
modern factory construction (fig. 1) permit of an adequate and
nearly uniform daylight illumination of the entire floor area, and are
desirable when practicable. When rooms are illuminated through
side windows, it is often difficult or impossible satisfactorily to light
all parts of the floor space, or to furnish adequate illumination to some
of the workers without furnishing too much to others, or without sub­
jecting the latter to objectionable glare. In some cases the use of
prismatic glass which redirects the rays of light so as to admit more
daylight into the room, especially into the parts of the room remote
from the windows, is worth while. As a rule it is better to confine the
prismatic glass to the upper sash of a window, as its use in the lower
sash is likely to cause objectionable glare; moreover it cuts off all view
of out of doors.
Windows should be equipped with adjustable devices so that the
illumination may be accommodated to changing exterior conditions.
Translucent window shades of light tones constitute the most im­
portant of these devices. Window shades or other daylight adjusting
devices should not be left to the mercy of those workers who may be
nearest the windows, but should be controlled by the room foreman.
He should readjust the window equipment for the varying daylight
conditions, and he should also decide when the use of artificial light
to make up for a deficiency in daylight in any location, is permissible.
Because of the time required for the adaptation of the eye to its
surroundings special danger is present when one steps from outdoor
sunlight into a dimly lighted storage space; for example, a passageway
connecting two well-lighted areas must be well illuminated. Again,
where the eye has been afforded the advantages 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 artificial lighting alone.
.— The proper and adequate main­
tenance of equipment for both natural and artificial lighting is essential.
Systems which are adequate when first installed will soon deterio­
rate unless properly maintained. 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 lighting 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

Maintenance of illum ination




CODE OF LIGHTING FOR FACTORIES, MILLS, ETC.

9

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 2 and 3 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 re­
quired 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 factory

MAINTENANCE. RECORD

7

JA N FEB MAR APR MAY
19 i If i IS / I f
1 If
12 n /a. lls as HSas as as HO

JU N JU L AU6 SEP <XX NOV DEC
f IS i i s / IS / i f / i f / i f / IS

w

H
Oao to

HO

f f 8 8 f I f i s i s 7f 70
*
f>
r 8 s t M 7S So S £

10 lo 70 70

l

8 f 8

r t 9 t ?.r I f t i s IS 10
t » IS i f 7i •*
t 9
7
t 2 2 » i s I f Zf 7.51 I f 70

m

70

T T.o To
o

7.o

To la 70

frfr

?o T

35V I f IS 7»" 7« 7o 7o T 7P to 7.0
®
9 V S W
|3 8 8 l t «

10 lo
9 8

I f IS 7.r i s 7o To 7p to 1.07-0
•
•
< tkJk(&n*.5to ? t t i VS IS IS IS IS 7.0
S
2 2. x x 7. ■x 4 . X 21 /)
l-k ifiw f

10 la

Z 2 2 fs X 2 2 X X. i.f

IS f f

-

"/ '

7-S

U
T
O7e
IS I f

i f 6f Cf SS

70

lo

2
2 2. ■. 2
2

F i g . 3.— L ig h tin g m a in te n a n ce record.

some instrument with which the foot-candles of illumination received
at any point can actually be measured. There are a number of
such instruments on the market, some of which, in the hands of
experienced men, are capable of a high degree of accuracy. One
instrument, the foot-candle meter (fig. 4), is not designed for precise
measurements, but nevertheless, has a considerable field of useful­
ness because its determinations are easily made and are accurate
enough for many practical purposes. The foot-candle meter is
small, light in weight, and does not require technical training for its
operation; foot-candle illumination is read directly from the scale
without computation or adjustment. 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 6




CODE OF LIGHTING FOR FACTORIES, MILLS, ETC,

F ig. 4.—A survey of actual lighting conditions can readily be made with the
foot-candle meter. This instrument is very useful in “ checking up” a light­
ing system to see that it is being properly maintained.




CODE OF LIGHTING FOR FACTORIES, MILLS, ETC.

11

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 gas and
electrical energy.
L oca tin g switches and controls.— The switches which turn on and
off the light in the entrances and halls of a building should be located
near the points of entrance. Likewise switches which control at
least one circuit of lamps in a room should be located near the principal
points 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 relative
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.
Control parallel to w indow s. — The light from the lamps most
distant from the windows will usually be required at times when the
natural light near the windows is entirely adequate, thus making it
advantageous to arrange the groups of lamps in circuits parallel to
the windows. The advantage of this method is further apparent
when it is considered that if the lamps are controlled in rows per­
pendicular to the windows all lamps in a row will necessarily be on
at one time, while a portion only may be required.
NOTES ON RULE 2.— AVOIDANCE OF 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 of 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. On the other hand, in inter­
preting and enforcing the glare rule the inspector is not expected to
insist upon what he may believe to be desirable practice in the given
case. His duty is only to insure the absence of a condition which is
prejudicial either to the health or to the safety of the worker.
If a simple instrument were available for measuring glare fhe task
of the inspector would be comparatively easy. However, there are so
many factors entering into the situation that it has not been found
practicable to develop any instrument which will properly evaluate
them all. To arrive at an intelligent judgment in any given case,
therefore, the inspector must be reasonably familiar with the prin­
cipal factors in or causes of glare.




CODE OF LIGHTING FOR FACTORIES, MILLS, ETC.

F ig . 5.—W henever local lighting is used it should be supplemented b y some general illumination. N ote the absence of glare and contrast between
light and dark areas in this room as com pared with Figure 7, where there is no general illum ination. In the above photograph, although a
local lam p is supplied for each machine, the individual sources of light are scarcely apparent, because of the general Illumination.




CODE OE LIGHTING EOR FACTORIES, MILLS, ETC.

13

CAUSES OF GLARE.

There are five principal causes of glare:
1.
.— The light source may be too bright; that
is, it may give off 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.
— The light source may be too powerful
comfort; that is, it may give off too great a total candlepower in the
direction of the eye.
Too frequently glare is assumed to be entirely a question of the
brightness 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
ahead of the observer will prove quite as glaring as the exposed fila­
ment 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 consequently 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 candlepower 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

Brightness of source

Total volume of lig h t

sky.

Location in the field of view

io f

3.
.— 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.
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 unobjection­
able at a distance of 8 feet from the eye provided this distance was
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 annoy­
ance 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 usually 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 at all, must be particularly well screened.
31517°—23----- 3




14

CODE OF LIGHTING FOR FACTORIES, M ILLS, ETC.

4. Contrast with background.— T h e contrast may be too great
between 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. A light background requires, first, that the surface
should be painted in a color which will reflect a considerable portion
of the light which strikes it; and, second, that the system of illumina­
tion employed should be such as to direct some light upon the back­
ground. In many cases the ceiling appears almost black under
artificial light simply because no light reaches it. W ith 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 high side walls and a paint of medium reflecting
power for the lower side walls will ordinarily be found most satisfac­
tory 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 look­
ing 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 condi­
tion 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 unde­
sirable contrasts.
5. Tim e o f exposure .— The time of exposure may be too great— that
is, the eye may be subjected to the strain caused by a fight 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 considerable 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.
RATING LIGHT SOURCES FROM THE GLARE STANDPOINT.

It is evident that the first two factors mentioned as causes of glare,
namely, excessive brightness and excessive candlepower, concern the
light source itself, the third factor concerns its location in the field of
view; and the fourth and fifth depend upon the conditions of its use.
In Table III a means of rating light sources (into Grades I to X )
has been provided which takes into account both their brightness




15

CODE OF L IG H T IN G FOR FACTORIES, M IL L S , ETC.

and their candlepower. Light sources in Grades I and II may be
termed soft or well diffused; those in Grades V III, I X , and X are
harsh and likely to cause glare. It is seen from Table III that a light
source of high intrinsic brightness but of low candlepower— for
example, one that would be classified under the fifth line of the first
column (less than 20 candlepower, and 100 to 1,000 candlepower per
square inch) has the same rating, Grade V , as a .source of lower
brightness but of greater total candlepower (2 to 5 candlepower per
square inch and 500 total candlepower) which falls in the second
line of the fifth column.
TABLE m .
CLASSIFICATION

OF LIG H T SOURCES FROM THE
GLARE.

STANDPOINT OF

Grade I indicates sources of m axim um softness; Grade X indicates sources of m axim um harshness.

Total candlepower in direction of eye.
Maximum visible brightness (apparent
candles per square inch).

20 to 50

50 to 150

150 to 500

500 to 2,000

Grade.

Less than 2........................................................
2 to 5 ...................................................................
5 to 20..................................................................
20 to 100..............................................................
100 to 1,000.........................................................
1,000 and u p .......................................................

Less than
20

Grade.

Grade.

Grade.

Grade .

I
II
II
IV
V
VI

I
II
III
V
VI
V II

II
III
IV
VI
V II
V III

II
IV
VI
V II
V III
IX

I ll
V
V II
V III
IX
X

In accordance with the plan of Table III, measurements of bright­
ness and candlepower have been made on a number of light sources
found in every-day practice, both natural and artificial, and grades
have been assigned to them as shown in Table IV . While engaged
in his work, the inspector will, of course, find other light sources in
use which are not included in the table; however, from those which are
given he should be able to estimate closely in what grades the others
should be placed. In cases of doubt, it is, of course, possible to
have actual measurements made to determine both the brightness
of the lighting unit and its total candlepower. The unit can then be
rated in accordance with Table III.
TABLE IV.
SPECIFIC CLASSIFICATION OF LIG H T SOURCES FROM TH E STANDPOINT
OF GLARE AS D ER IV E D FROM TAB LE III.
N a t u r a l L ig h t S o u r c e s .

(As seen through windows or skylights.)
Grade.

Sun.........................................
Very bright sk y ...................
Dull sky................................
Sun showing on prism glass




Open Gas F lames .

X
V
III
IX

II

16

CODE OP LIGHTING FOE FACTORIES, M ILLS, ETC,
I n candescent M an tle G a s L am ps.

Mantles
Mantles
Large single Large single Cluster or high
consuming consuming mantle or
mantle or pressure lam p
2-5 cubic
5-8 cubic
cluster 8-12 cluster 12-20 consuming
feet per
feet per
cubic feet
cubic feet above 20 cubic
hour;
hour.
per hour.
per hour.
feet per hour.
Gtdde.

Grade.

Gfade.

Grdde.

Grade.

V
III
II
I

VI
IV
III
II

V II

v lii

IX

I V -V I
III-V

V -V H

Clear glassware........_________________
Frosted globes..........................................
6-inch opal globe......................................
8-inch opal g lob e1...................................
10-inch opal glob e1.................................
12-inch opal glob e1.................................
Dom e reflector:
Mantle visible...................................
Mantle not visible............................
B ow l reflector:
M
q.Tit.lp. visible...................................
Mantle not visible............................
Totally in d irect1.....................................
Semi-indirect b o w ls 1..............................

V I -V I I I
V
I

VI
II

V II
III

vm
rv

IX
IV

V
II

VI
II

V II
III
I -I I
H -m

V III
v

IX
V
III
H I -V I

ii

H -I V

1 Where a range is given, the best grade, that is the lowest, applies to globes that are evenly luminous, and
the poorest to globes which have a decidedly bright spot in the center.
A

rc

L am ps.
Grade.

IX
X
V II-V I I I

Inclosed arcs, clear globes
Flame arc, clear g lo b e s .. .
Flame arc, opal globes—
M ercury V
Car bo n

and

T

apor

VI

ubes

M e t a l l iz e d F il a m e n t I n c a n d e s c e n t L a m p s .

8 candlepower....................................................................................
16 candlepower..................................................................................
32 candlepower..........................................................................................

T

u ngsten

V
V
VI

F il a m e n t I n c a n d e s c e n t L a m p s .

W atts.

300

500 to
1,000

Grade.

Grade.

Grade.

IX
V II
I V -V I
I I -V
I I -V
IX

IX
V I II

X

I V -V I
I V -V I
IX

V I I-V I I I
V -V I I
X

V III

IX

IX

III

III

rv

V II

V III

IX

IX

X

II

III
IV
I I I -IV
I -I I
I -I I I

IV
V
I V -V I
I -I I
I I -I II

VI
VI
I V -V I I

V II
VI
V I -V I I I
III
II I -V I

75 to 100 150 to 200

10 to 25

Grade.

Bare lam ps........................................................
Frosted lamps or frosted globes....................
8-inch opal $ ob es *..........................................
12-inch opal glob es1........................................
16-inch opal globes *........................................
Flat reflectors—filament visible...................
Dom e reflectors—steel or dense glass:
Filament visible from workingposition.
Filament not visible from working
position...................................................
B ow l reflectors—steel or dense glass:
Filament visible from working position.
Filam ent not visible from working
p osition...................................................
D om e reflectors—bowl-enameled la m p s ...
Semi-inclosing u n its1.....................................
Totally indirect lighting1..............................
Semi-indirect bow l i ................- .....................

40 to 60

Grade.

Grade.

VI
II

V II
III

I-II

V III
VI
I I -I V
I I -I I I

VI

Vii*

V III

VI

V II

I

I

VI
II

I

ii

I I -I V

X
VI

i Where a range is given, the best grade, that is the lowest, applies to globes that are evenly luminous,
and the poorest to globes which have a decidedly bright spot in the center.




CODE OE LIGHTING FOR FACTORIES, MILLS, ETC,




18

CODE OF L IG H T IN G FOE FACTORIES, M IL L S , ETC.

TABLE V.
CHART OF THE FIELD OF VIEW .
C L A S S IF I C A T I O N O F P O S I T I O N O F L I G H T S O U R C E W H I C H T A K E S I N T O A C C O U N T T H E
D IS T A N C E F R O M T H E E Y E A N D T H E A N G L E O F T H E L IN E O F V IS IO N S

H orizon tal distance o f ligh t source fro m observer, in feet.
H eigh t a bov e
floor, in feet.
1

2

3

4

6

8

10

12

16

20

25

30

35

40

50

60
an d
up.

6.5 or le s s ............... 2 A
6.5 t o 7 ....................
G
7 t o 8........................ G
8 t o 9........................ G
9 t o 10...................... G
10 t o 11.................... G
11 t o 12.................... G
12 t o 13.................... G
13 t o 14.................... G
14 t o 15...................
G
15 t o 16.................... G
16 t o 17.................... G
17 t o 18.................... G
G
18 t o 1 9 ...'..............
19 t o 20 an d u p . . . G

2A
E
G
G
G
G
G
G
G
G
G
G
G
G
G

A
D
F
G
G
G
G
G
G
G
G
G
G
G
G

A
C
E
F
G
G
G
G
G
G
G
G
G
G
G

A
C
D
F
F
G
G
G
G
G
G
G
G
G
G

A
B
D
E
F
F
F
G
G
G
G
G
G
G
G

A
B
C
D
E
F
F
F
G
G
G
G
G
G
G

A
B
C
D
E
F
F
F
G
G
G
G
G
G
G

A
B
C
C
E
E
F
F
F
G
G
G
G
G
G

A
B
C
C
D
E
F
F
F
F
F
G
G
G
G

A
B
C
C
D
D
E
E
F
F
F
F
G
G
G

A
B
C
C
D
D
E
E
F
F
F
F
G
G
G

B
B
C
C
D
D
D
E
E
F
F
F
F
G
G

B
B
C
C
D
D
D
E
E
E
E
F
F
G
G

B
B
C
C
D
D
D
E
E
E
E
E
F
G
G

B
C
C
D
D
D
D
E
E
E
E
E
F
F
G

1 See F ig . 6.
8 Classified as A unless ligh t source is so n ea rly a b o v e th e head o f operator as t o b e q u ite ou tside o f field
o f v iew , in w h ich case classify as E .

TABLE VI.
SHOWING LIM ITING GRADES OF LIG H T SOURCES PERM ISSIBLE FOR
VARIOUS SOURCES. '
S pace or w ork t o b e ligh ted .

Classification o f p o sition .

R oadw ays
an d y a rd
thoroughfares.

Offices a n d
Storage spaces,
O rd in ary
d ra ftin g w o rk
aisles, stair­
w a y s, han dlin g m an ufacturing
a n d certain
op era tion s.1 m an u fa ctu rin g
coarse m ate­
o p e ra tio n s.2
rial.

Limiting grade. Limiting grade. Limiting grade. Limiting grade.
A ..........................................................................
B ..........................................................................
C ...........................................................................
D ...........................................................................
E ..........................................................................
F ...........................................................................
G ...........................................................................

VI
V II
V III
IX
IX
X
X

VI
V II
V III
IX
X
X

I ll
V
VI
V II
V III
IX
X

II
IV
V
VI
V II
V III
X

1 F o r th e p resent th e lim its set in this tab le ca n n o t b e r ig id ly a p p lie d t o p orta ble la m p s used for te m p o ­
ra ry w ork , su ch as s etting u p m achines, repairing a u tom ob iles, etc.
2 T h os e operation s in w h ic h w orkers are seated facin g in on e direction for lo n g periods o f tim e.
B a ckg ro u n d .

Where the background and the surroundings are very dark in tone,
a light source of one grade softer than that specified in Table V I may
be required. Where the background and surroundings are very light
in tone, one grade more harsh than that specified in the table may
sometimes be permitted.
From a study of Table IV it will be observed that incandescent
lamps equipped with reflectors which do not completely hide the
light source have been assigned to the same grade as the corres­
ponding sizes of bare lamps. It is true that the addition of a reflector
somewhat increases the total candlepower in the direction of the eye
and therefore the argument might be advanced that a 100-watt
lamp with a flat reflector should be classified in Grade I X whereas



CODE OF L IG H T IN G FOB FACTORIES, M IL L S , ETC,

a n d 8 .— A d join in g room s in th e sam e fa cto ry. T h e u p p er figure illustrates a
s trictly local ligh tin g system o f th e p oorer sort. T h e lo w e r figure illustrates a lighting
system consisting o f 150-watt b o w l enam eled lam p s e q u ip p e d w ith d o m e reflectors
spaced 10 feet apart; th e average illu m in ation is 9 foot-candles.

F ig s . 7




19

20

CODE OF L IG H T IN G FOR FACTORIES, M IL L S , ETC.

the bare lamp is Grade V III. On the other hand, from the stand­
point of glare, the effect of the light background furnished by the
reflector at least compensates for the increased candlepower which it
gives; the rating is therefore kept at Grade V III.
.— It has already been pointed out that
the distance between a light source and the eye, and its angle to the
line of vision have much to do with determining how bright a light
source may be used without discomfort. In Table V, which is a
chart of the field of view, the possible locations of light sources are
classified in seven groups, A to G inclusive, depending upon their
distance from the eye and their proximity to the line of vision.
Light sources in positions designated A , B, or C, are close to the eye
or close to the line of vision; hence they are most likely to be the
cause of discomfort, and the greatest care must be exercised in their
selection. In positions F and G, on the other hand, the use of
bright sources is much less harmful.
.— Table V I shows the
harshest grade of light source which should be permitted within the
field of vision for fixed conditions as to location of lamp, brightness
of background, and character of work performed.
The grades named in Table V I are definitely limiting values and
in each case the use of softer light sources is to be recommended;
that is, where Grade IV is permitted, the installation of a lighting
unit of Grade II or of Grade III will be conducive to better results
as regards both accuracy of vision and eye comfort.
From Table IV the majority of bare incandescent lamps are seen
to have a relatively poor rating— that is, most of them fall in Grades
V II to I X — and it is evident from Table V I that Grades V II to I X
are never to be permitted in workrooms in positions A , B, or C;
that is, the use of bare incandescent lamps is prohibited in working
areas except when they are located at considerable heights above
the floor or when they are so placed as to be out of the field of vision.
A t the present time it will be found necessary from a practicable
standpoint to delay the strict enforcement of this provision in a
very few instances, particularly in the case of extension cord lamps
used in temporary work, such as in setting up machinery and in
r e p a irin g automobiles, etc.
It will be noted from Table IV that the sources of natural light,
side and ceiling windows, usually fall ih Grade IV . This means
(see Table V I) that no mandatory rules are established as to the use
of shades, awnings, etc., except in those cases where the sky is visible
through portions of the sash in position A ; that is, less than 6.5 feet
above the floor, or where the sun itself comes within the range of
vision.
.
However, Grade II is the limiting value for light sources less than
6.5 feet high,An offices, and other locations where the workers are
seated facing in one direction for considerable periods of time. Hence
in these cases, to comply with the table, the work must be so arranged
that the employees are not required to face windows where the sky
is visible through the lower sash; that is, less than 6.5 feet above
the floor.
Prism glass when so located as to catch the sun’s rays ordinarily
has a very much poorer rating than clear glass; hence, where it is
used the installation of window shades or curtains should ordinarily
be required.

Charting the field of view

relatively

Lim iting grades fo r specific installations




CODE OF L IG H T IN G FOB FACTORIES, M IL L S , ETC,

F ig . 9.— Glaring ligh t fro m u n sh ad ed lo ca l la m p w h ich is a m enace t o safety an d t o v ision,
a n d is one of th e evils w h ic h th e L igh tin g C ode is e xp e cte d t o elim inate.

"Fi g . 10.— L igh ting' an office b y m eans o f indirect un its.
foot-candles.




Illu m in ation a p p ro x im a te ly 6

21

22

CODE OF L IG H T IN G FOR FACTORIES, M IL L S, ETC.

The question naturally arises why, if glare is so objectionable,
should not all sources capable of producing glare be prohibited
everywhere. The answer is that to attain a maximum softness of
light sometimes entails a sacrifice in efficiency and an increase in
operating expense. If a worker chooses unnecessarily to gaze
directly upward at bright skylight or at an artificial lighting unit so
located that it is not a factor in glare under ordinary circumstances,
it is scarcely within the province of code a of lighting to protect him
from the consequences.
.— To determine whether a given
lighting installation is within the glare limits specified, proceed as
follows:
(1) Select what appears to be the most glaring light source within
the field of view of any of the employees when at work. Measure
the height of that light source above the floor and its horizontal dis­
tance from the worker.
(2) W ith the height and distance find in Table V how this location
in the field of view is classified (position A, B, or C, etc.).
(3) W ith the classification of the position fixed from (2), determine
from the proper column of Table V I the harshest grade of light source
ordinarily permissible for this location.
(4) If surroundings are very light or very dark, apply a correction
of one grade (plus or minus) to the value found in (3).
(5) From Table IV find the classification of the light source in use
and compare with (4). (If the particular source is not listed, its
grade may be estimated or may be determined by actual photometric
measurements.)
.— Another way in which glare is produced is by
the reflection of light from polished surfaces in the field of vision.
The difficulty experienced 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 wav 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 semiindirect 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 concen­
trated light 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.

How to use Tables IV , V, and V I

Glare by reflection

NOTES ON RULE 3.— EXIT AND EMERGENCY LIGHTING.

The employer is to be held responsible for the proper lighting of
passageways, stairways, and exits, in so far as his premises are con­
cerned, which means such parts of buildings, floors, or rooms as are
controlled by the employer, including entrances thereto, but exclud-




CODE OF L IG H T IN G FOB FACTORIES, M IL L S, ETC,

F i g . 1 1 — D raftin g-room lighting, using dense sem i-indirect un its a n d 200-watt la m p s

F ig . 12.-"-A ya rd ligh tin g in s ta lla tio n con sisting o f '150-w a tt la m p s in shallow b o w l reflec­
tors, m ou n ted 20 feet fr o m th e g ro u n d . T h e units in each row are s pa ced 60 feet apart,
a n d th e t w o row s are 30 feet a part.




23

24

CODE OF L IG H T IN G FOR FACTORIES, M IL L S , ETC.

ing hallways, passageways, and stairways giving access to other
floors, or to spaces on the same floor, and used in common by the ten­
ants of the building. These latter shall be lighted by the party or
parties in control of the building, in accordance with the code, and
the following provisions and interpretations thereof:
“ Exit and emergency light sources7 are to be understood as those
’
artificial illuminants which are necessary only to make clear to the
occupants or employees the regular places of exit, or to enable them
to pass to and along safe exits with reasonable speed and assurance
of looting. Such lighting is never assumed as being necessarily suffi­
cient for the proper performance of regular working operations.
The circuits for exit and emergency electric lamps should be wired
to be independent of the working lamps, back at least as far as the
branch panel or distributing board, and should be separately fused, so
that any failure of the regular working lamps through causes arising
within that working space will not also cause failure of the exit,
stairway, or passageway lamps.
No fuses smaller than those of the emergency branch circuits shall
be used back of (that is, on transformer, meter, or generator side of)
such circuits, and no power machinery, portable extension cords, or
convenience outlets shall be on such emergency circuits.
The “ main service entrance” may be interpreted to mean the
entrance point (meter or distributing panel) oi lighting feeders for
the building, floor, loft, or particular space in question. In gas light­
ing 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.
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 the 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
as or other reasonably dependable illuminant. Under normal conitions, however, the phrase “ separate supply” shall, in electric
service, be interpreted to mean a separate branch circuit which will
afford lighting as long as transformers, generators or main lighting
feeders are intact; and in gas service, interpreted to mean branch
piping extending back to a sufficiently large feeder to insure a gas
supply unless stoppage occurs near or outside of the main gas meter.
As indicated in the general requirements under Part I of this code,
the exit and emergency lamps should be lighted whenever artificial
lighting is required in the work spaces.
It is the obvious intent of Rule III 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 and sundry types and situations of working
spaces, must be reached through mutual cooperation of the owner
and the State authorities.

§




CODE OF L IG H T IN G FOR FACTORIES, M IL L S , ETC,

F ig . 13 — L igh tin g of steel rolls. Illu m in a tio n p r o v id e d b y fiv e m an tle in closed gas arc
la m p s, e q u ip p e d w ith op a qu e reflectors.

F ig . 1 4 — Shirt-w aist fa cto ry, sew ing-m achine lighting. Illu m in ation p r o v id e d b y single­
m an tle gas lam ps, eq u ip p e d w ith prism atic reflectors. L a m p s spaced 9 feet apart, w ith
a clearance of 5 feet a b o v e w orking plane.




25

PART III.—ADVANTAGES OF GOOD ILLUMINATION.
While the advisability of good natural and artificial illumination
is so evident that a list of its effects may seem commonplace, these
effects are of such importance in their relation to factory manage­
ment that they are worthy of careful attention. The effects of good
illumination, 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 for the same labor cost.
4. Less eyestrain.
5. Greater contentment of the workmen.
6. More order and neatness in the plant.
7. Supervision of the men made easier.
While it is difficult to place a definite money value on the savings
effected in increased production and improved quality, by good
illumination, it by no means follows that such savings are insig­
nificant or unsubstantial. The factory owner who ignores them
neglects his own interests. Other items in the foregoing fist, even
more difficult to value definitely, are none the less real; taken together,
they constitute a powerful argument in favor of the best available
illumination in the factory.
The following estimate, conservatively based on practical condi­
tions, gives an idea of the relative costs of good illumination by arti­
ficial means, and of labor, in the factory.
Assume that the lamps are so spaced that one 100-watt incandes­
cent electric lamp will take care of one operator; that in this particular
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 p r ic e )................................................
Cost of wiring per outlet....................................................................................

$1.10
2. 50
8. 00

Total investment..................................................................... : .....................

11. 60

Cost of operating per annum:
Interest on investment, $11.60, at 6 per cen t...............................................
Depreciation on reflector and wiring, at 12J per cent.................................

.70
1. 31

Renewal of lamp O o f iX * 1-10...................................................................................... 66
Cleaning, at 3 cents per cleaning, two per m onth.......................................
Energy, at 5 cents per kilowatt-hour..............................................................

.72
3. 00

Total annual cost of maintaining good illumination:
Per man per year................................................................................................
6. 39
Cost of labor: Annual wages per man per year:
8 hours, at 45 cents per hour; 8X300X10.45................................................ 1, 080. 00
26




CODE OF L IG H T IN G FOR FACTORIES, M IL L S , ETC,

Fig. 15.—A plant where machine tools are manufactured, using mercury vapor lamps spaced
20 feet apart at a height of 25 feet above the floor; approximately 1 watt per square foot.

Fig. 16.—Laundry lighting. Illumination provided by five mantle gas arc lamps, in­
closed type, equipped with diffusing glass globes.




27

28

CODE OF L IG H T IN G FOR FACTORIES, M IL L S , ETC.

If an operator, because of the good illumination, saves— in more
production, or better quality of product— the equivalent of only three
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 estimated 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 ten times the cost
of giving him good illumination.
The factory owner, when approached by the gas or electric lamp
salesman, should weigh carefully any argument in favor 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 ior 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
though 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.
ACCIDENT INSURANCE COSTS.

Compensation insurance premiums for a given plant are based on
the amount of the pay roll, and the rate is determined by the accident
experience of a given industry, modified by the experience of the
particular plant under consideration. W ith a rate of 1 per cent
the annual premium in the case of 1,000 employees at an average
wage of $40 per week would be $20,800.
An insurance carrier might pay the claims resulting from two
accidents per month (on an average) in this plant, and meet his
own overhead costs, and still have a slight margin of profit. An
experience of three accidents per month, one-third of them due to
poor lighting (a not unlikely event), would probably leave the
insurance carrier no option but to increase the rate, by, say, 50 per
cent. The premium would then be $31,200— an increase of $10,400.
If the lighting costs only $3 per employee or $3,000 per year total,
the owner’s annual expense for poor illumination actually amounts
to $13,400— of which $10,400 is required by the insurance company
to meet accident claims. An expenditure of $6 per year per em-*
ployee for lamps and energy might save a large portion, if not all,
of the latter amount.




INDEX.

Accident:
Hazards due to poor ligh t. . .
Insurance costs........................
Loss of tim e due t o ................
Reduction o f............................
Advantages of good illumination
Aisles. (S ee Passageways.)
Artificial illumination:
A m ount required....................
Combination w ith natural...

Page.
24
28

Insurance accident cost......................................

Page.
28

1,2

Lamps, bare.........................................................

20

1,2

26,28
3,4

8

Background:
. Contrasts.........................................................
14
Evaluation o f................................................
18
Bare lam ps............................................................
20
Brightness of light source:
Causes of glare............................................... 13,14
14
Ceiling, color o f ....................................................
8
Repainting...............................................
Charting field o f v iew ......................................... 17-20
Classification of light sources from standpoint
of glare............................................................... 15-20
8
Cleaning reflectors and lam ps...........................
14
Color of walls and ceilings.................................
14
Contrast w ith background................................
Control:
11
Locating o f switches a n d ............................
11
Parallel to w indow s.....................................
Cost of ligh t.......................................................... 26,28
Daylight. ( See W indows; Saw-tooth roof
construction; Prismatic glass; Outdoor il­
lum ination.)
Depreciation due to dirt....................................
9
3
Diffusion and distribution o f ligh t..................
E conom y o f good illum ination........................... 26,28
Energy consumption, importance o f...............
28
E xit and emergency lighting........................ 3,22,24
Field of view , charting th e .......................... 17,18,20
Foot-candle:
6
Definition......................................................
Measuring instrum ents...............................
9
V alues recomm ended..................................
4-6
Values required............................................
3
Fuses for exit and emergency lighting....................... 24
Glare:
Avoidance o f................................................. 3,11
Causes o f.........................................................
13
Brightness o f source.............................
13
Total volum e o f light............................
13
Location in the field o f view ...............
13
Contrast w ith background..................
14
Tim e o f exposure...................................
14
Classification of light sources from stand­
point o f....................................................... 14-20
Defined...........................................................
11
Limits, determination o f............................
22
Objectionable features o f............................
11
Rating of light sources from standpoint of. 14-16
Reflected........................................................
22
Illumination:
Advantages of good ........................................26,28
9
Measurement o f............................................
Maintenance o f.............................................
8,9
N atural...........................................................6,8,20
Natural and artificial com bined................
8
Outdoor..........................................................
8
Operations not requiring............................
6
O f passageways............................................. 8,22
Planes o f . ......................................................
6
Range o f.........................................................
6,8
Required foot-candle values......................
3,4




O

Cost o f...............................................................26-28
Diffusion and distribution o f .....................
3
Excess of, causing glare......................... 13,14,15
Operations performed w ithout ligh t........
6
Light sources:
Brightness of, causing glare.................. 13,14,15
Classification from standpoint of glare. 15,16,20
Lim iting grades permissible for various
locations......................................................
18
Lim iting grades permissible for specific
20
locations.....................................................
Location in the field of view, causing
glare.............................................................
13
Lighting:
E xit and em ergency...................................3,22,24
L oca l...............................................................
14
Natural. (See W indows; Saw-tooth roof;
Prismatic glass.)
Local lighting......................................................... 13,14
Locating switches and controls........................
11
Location o f light sources in field of v ie w ........ 13,14
Losses due to poor illumination.......................
28
Maintenance.........................................................
Checking foot-candle values.......................
Measurement o f illumination............................

8,9
9,11
9,11

Natural lighting. (See W indows; Saw-tooth
roof construction; Prismatic glass.)
Natural and artificial lighting, combination
o f.........................................................................

8

Operations performed without light or b y
their ow n li^ht.................................................
Outdoor illumination.........................................

6
8

Painting walls and ceiling.................................
8
Passageways, illumination o f.......................... 8,22,24
6
Planes o f illumination........................................
Prismatic glass..................................................... 8,20
Production increase due to better ligh t..................... 26
Rating of light sources from standpoint of
glare...................................................................... 14-16
Recommended foot-candle values....................
4
Reflected glare.....................................................
22
Required foot-candle values..............................
3
R ules......................................................................
3
Avoidance of glare........................................
3
Diffusion and distribution of light...........
3
E xit and emergency lighting.....................
3
Illumination required, foot-candles..........
3
Saw-tooth roof......................................................
8
Shades for w indow s...........................................8,13,20
Shadows................................................................
22
State codes............................................................
1
Reasons for....................................................
1
Switches and controls.........................................
11
V is io n ..-................................................................

1

Walls, color o f......................................................
Walls, repainting.................................................
W indow s...............................................................
W indows, shading o f..........................................

14
8
8,20
8,13

29


Federal Reserve Bank of St. Louis, One Federal Reserve Bank Plaza, St. Louis, MO 63102