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UNITED STATES DEPARTMENT OF AGRICULTURE

I

U Agricultural Research Service;/

AGRICULTURE HANDBOOK No. 37
"ü%^\

Prepared by the safety committees of

Utilization Research Branches of the

Agricultural Research Service

UNITED STATES GOVERNMENT PRINTING OFFICE .Washington. P. C, 1954^

For sale by the Superintendent of Documents, Washington 25, D. C. — Price 20 cents
Manual on Safety

for Workers in:

Chemical Laboratories

Pilot Plants

Chemical Storerooms^

Mechanical Shops

• -3-

UNITED STATES DEPARTAÎENT OF ACRICl LTl RE

Agricullural Research Service

AGRICULTURE HANDBOOK NO. 37
CONTENTS

Good safety practices '

Hazardous chemicals ^

Storage and handling 11

Disposal 12

Fumigants 13

Glassware and glass apparatus 1'*

Vacuum systems 15

Pre sure reactions and pressure equipment 16

High-pressure technique 17

Compressed gas containers .• 18

Flammable materials 20

Electrical installations 22

Process equipment 23

Miscellaneous laboratory and pilot-plant technique 24

Mechanical and shop equipment 26

General precautions 26

Specific machines and equipment 27

Care of machines 30

Care of tools 30

Handling equipment and material 31

Housekeeping 31

Office and miscellaneous hazards 32

Protective equipment for personnel '. 32

Appendix 33

Issued June 1954

ii
CAUTION

The instructions in this manual are for the protection of you and your fellow employees. By familiarizint: vourself with and following them you can prevent

manv accidents and injuries.

The manual covers not only the usual hazards in

the laboratory, the pilot plant, the chemical storeroom,

and the shop, but also some less common hazards.

Theoretically, it may be said that all accidents are

avoidable. Two major types are generally recognized:

Those—the most frequent—which would not have

happened had adequate care been exercised by the

operator; and those caused by unforeseen failure of materials of construction or deviation of reactions from

the expected course. Experience shows that in the performance of all laboratory operations there is usually

a best way, which is also the safest. Al^'ays conduct

any potentially hazardous operation with maximum

protection. Even though you have conducted it several

times without mishap, never relax your vigilance or

dispense with any safeguard.

The responsibilit)' for preventing accidents extends

from the top of the organization all the way down

to the mdividual worker. Section or group leaders

must see that workers under their supervision are informed of hazards which they may encounter and of

the safer/ precautions and proper techniques to be used.

No person or group should be entrusted with an operation bevond his or their capabilities. It is the obligation of each worker, who is the chief loser if hurt,

to follow the safety instructions that have been prepared

and are pertinent to his work. Nature provided us

with only one pair of eyes, hands, and feet, and they

were meant to last .i lifetime.

In case of doubt on any operation, a person carrying it out for the first time, or having but little laboratory experience, should first consult more experienced employees. Under no circumstances, except in

emergencies, should he e\er use apparatus or equipment in laboratories other than his own without the

knowledge and consent of the person immediately in

charge. The most simple equipment may be a serious

hazard in the hands of an inexperienced worker.

Be familiar with .md use, whenever necessary, personal protectne equipment, such as gloves, face shields,

goggles, aprons, respirators, gas masks, fire blankets,

and safety showers. You should also receive instruction, including demonstration, on the correct use and

operation of portable fire extinguishers that have been

provided for the area in which you are working.

Where unusual risk is involved, the number of individuals present should be kept at a minimum, but

never less than two persons. Both must be familiar

with the processes and necessary safety measures.

1
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.Vitvts1 Hous^*"" :keepi-^: >-'\::v''

Although a toiuinuDus concerted and organized effort is essential to prevent accidents, procedures and

means for prompt and effective action when a fire or

explosion occurs, or an employee is injured, are also

vitally important. This involves the following: Transmission of a fire alarm to the plant fire brigade and,

when necessary, to the city fire department; use of

fire fighting and safety equipment within the plant;

vacating affected areas; rescue of injured persons; administration of first aid; and, in case of serious injury,

medical treatment and hospitalization at the earliest

possible moment.

All employees should be well organized and properly trained, through the medium of appropriate committees, squads, and designated leaders, to perform

prescribed and assigned duties for safeguarding, to the

fullest extent possible, persons and property against fires,

explosions, and other accidents.

A suitable electrical system should also be installed

in cold rooms and other hazardous enclosures by means

of which an employee, trapped therein or otherwise

in distress, can transmit simultaneously both an audible and a visual alarm to a designated receiving station

within the plant.
, •'»as^-Äs.. .v,"

Hazardous Chemicals

Chemicals that disturb normal physiology may be

regarded as toxic. The fact that physiological effects

are not immediately apparent is no indication that a

chemical is harmless. Your body can absorb toxic materials by inhalation or by contact with the skin. Organic solvents of higher toxicity include the amyl derivatives, most of the chlorinated hydrocarbons, trichloroethylene. the homologues of benzene, chlorobenzene. and the hydrogenated cyclic hydrocarbons.

Those that are strongly poisonous include the methvl

linkages such as methyl alcohol, methyl chloride, dimethyl sulfate, tetra- and penta-chloroethane. benzene.

I only fiad one

acc/denf in my lift/ ''

and carbon disulhde. The vapors of some of these

compounds are also highlv explosive. Never allow

these compounds to evaporate into the laboratory air;

never keep them in open containers or heat them

without adequate means for condensing or disposing

oi the vapors.

Do not mix strong oxidizing agents, such as nitric

and perchloric acids, nitrates, and perchlorates, with

easily oxidizable materials, such as sulfur, sullides, and

organic chemicals, without proper care and realization

of the explosion hazard in\olved.

Have gas masks readily a\ailable

iVIake sure that your gas mask is readily available

and properly labeled. Where special gases such as ammonia or sulfur dioxide are a hazard, appropriately

marked masks should be provided for the specific service. The all-purpose or all-service gas mask will filter

out adsorb, or nei tralize nearly all poisonous smokes

or gases. However, it will not provide oxygen in an

oxygen-deficient atmosphere. Keep this in mind when

using the mask. ( A special mask supplies oxygen for

a number of hours.) All scientific personnel should

be informed as to the use, care, and location pf the

gas mask. Operating instructions and other pertinent
duta are given on ii card inside the ¿as mask box

cover. Each person concerned should try on the mask

to familiarize himself with the operation. After use,

the mask should be sterilized, either as directed on the

card with dilute formalin solution, or with 50 percent

ethyl alcohol. The alcohol is less irritating when a

number of persons are trying on the mask in succession. The mask should be put into the box carefully,

to avoid strain or crumpling of the rubber tubing.

Periodic inspections of the mask should be made and

the canisters should be replaced or returned to the

factory for refilling as needed.

Hoods should be used

Use a hood when evaporating acids and flammable

liquids and when working with toxic and poisonous

vapors or gases. They should also be used for ash tests

where fumes are given off, for decomposing chemicals

by means of acids, for boiling solutions containing

ammonia, hydrogen sulfide, etc., and for experimental

work involving explosion hazards. For maximum safety

It is essential that hoods be operated with the front

windows closed.

Every new chemical prepared in the laboratory should

be considered a hazardous material until its properties

have been determined. Detailed information on the

toxicity of specific chemicals can often be obtained

from the National Institutes of Health, Bethesda, Md.

Some hazardous chemicals used m lahoratory work

Acetal

Use acetal cautiously when working with old samples

because of the possibility of an explosion. Such an explosion ( reported in Chemical and Engineering News

for June 25, 1944) accompanied the distillation of a

specimen of diethylacetal which had been stored for

an indeterminate period in amber glass and in complete darkness. After collection of a considerable forerun that appeared to be alcohol, and when acetal was

just beginning to come over, an explosion of great

violence occurred. It was not accompanied by flame

and appeared to take place in the vapor phase, as the

stillhead and condenser were shattered, but the flask

remained intact.

Acrvlates

Store acrylates { methyl and ethyl acrylate monomers)

in a CO(J1, dark place. Without an inhibitor the monomers, may be destroyed with explosive violence. Table

1 shows the time required for destruction of ethyl

acrylate at various storage temperatures with and without an inhibitor. Other acrylate monomers behave similarly.
Table 1 INHIBITOR TEMPERATURE SHELF LIFE'

/Hydroquinone (14 percent)

Hydroquinone {'A percent) ....

Hydroquinone {'A percent). . . .

None

None

None

None

None

None

°F

68- 86

68-122

68-140

176

158

140

122

104

32

12 months

4 months

3 months

1' 2 hours

20 hours

44 hours

116 hours

Over 116 hours

Over 5 months

'Not more than a two months' supply oí the monomer should he pLireh.iscJ If enough

monomer to last through the summer is in storage, .in atljiiional '.4 pere'ent hvdrtiqumone should

1 be added

Allvl chloride / o

-t DOR tm EYE

IRRITANT

AUyl chloride is toxic. Precautions are always necessary to avoid spillage of allyl halides and accumulation of noticeable concentrations of the vapors in the

atmosphere, as repeated exposure to the vapors has

serious effects, including damage to the lungs. Keep

the liquid off the skin and clothes. Maintain good venAluminum chloride

Aluminum chloride is potentially dangerous. If moisture is present, sufficient decomposition can build up

tilation. W'hen the odor of allyl halides is at all noticeable, use a gas mask equipped ^'ith an organic

vapor canister.

Seier disregard the iiannng odor or eye irritation

ni alhl halides}

MOISTURE =

PRESSURE

considerable pressure. If a bottle is to be opened after

lono; standing, enclose it completely in a heavy towel.

EXPLOSIVE WITH MERCURY

Ammonia

Ammonia with silver or mercury forms an explosive. mercury to dry; acidify and discard it at the first opNever place it in contact with these metals. Do not portuniry.

permit an ammiini.ical solution containing silver or

~Taken from "Ally! Chloride and Other Halides," Shell Corporation, New York. 1951). For further details .see pa,«es 85-S7.

5
Aniline POISON

Aniline is a poison and its fumes are readily absorbed. Large doses can cause convulsions and death.

Observe the following precautions: Use only the minimum amount required at a time. Wash off immediBenzene

Benzene \apors are very dangerous when inhaled.

Great care is essential m working with large quantities

of benzene to- avoid escape of the vapors into the surrounding atmosphere. Stills used fi.>r recovery of benatelv any spillage; use extreme care to avoid inhaling

the fumes. Remove immediately any clothing saturated

with aniline to prevent contact with the skin.

Castor-bean meal

Castor-bean meal or castor pomace and unmilled

castor beans contain a violenth' poisonous protein—

ricin—a nitrogenous component—ricinine—also poisonous, and a nonioxic, but exceptionally potent allergenic

protein. The physiologic activity of these components

Carbon disulfide

Because carbon disulfide is extremely flammable and

its vapors extremely explosive, it is one of the most

hazardous flammable solvents used in the labüratür\.

Use extreme care at all times when handling it. VaCaibon tetraehloride

Carbon tetraehloride gi\es oft" hydrochloric acid gas

at room temperature. It can be absorbed through the

Chlorinated hydrocarbons

Continual exposure to chlorinated hydrocarbons, even

in small amotmts, causes dermatitis and other body disorders. They act not only as defatting agents on the

DANGEROUS-TOXIC

zene should be in a special room or space that is

provided with sufficient ventilation to remove all vapors of benzene liberated.

TOXIC

warrant suitable precautions to preclude inhalation of

dust from the beans or pom.ace or the contamination of

edible products with them. Castor oil, apparently, contains none of these toxic or allergenic components.

FLAMMABLE

EXPLOSIVE '

pots of carbon disulfide may be ignited by exposed

steam pipes. The liquid may be ignited by static electricity when poured from one container into another.

For safety, both containers should be grounded.

^:E==^

GAS AT ROOM TEMPERATURE

skm. Use it only in a well-ventilated room. Never allow

it to come in contact with the skin.

DERMATITIS

skin, but are selectively absorbed by some organs of the

body. Avoid continual contact with ail such materials

either on the skin or by breathing.
Chlorine, bromine, iodine

Chlorine, bromine, and iodine produce very poisonous

vapors. Use only in a hood. Don't mix chemicals containing ammonia with chlorine or bromine; those containmg iodine or ammonia should not be mixed with

Dimethyl sulfate

Dimethyl sulfate is very reactive, especially when

it comes in contact with skin or mucous membrane. A

very short time of contact results in a painful burn.

Extreme caution should be exercised to prevent contact

^ POISONOUS

VAPORS

chlorides, bromides, or iodides in the presence of oxidizing agents. Extremely sensitive and dangerous nitrogen

trichloride, bromide, or iodide may be formed.

PAINFUL BURNS

with the eve tor on contact the sight could be impaired.

Inhalation of the vapors causes a toxic effect which may

be delayed but very se\ere. Never use this compound in

the open laboratory but always in a well-ventilated hood.

Dioxane

Dioxane ( diethylene dioxide) appears to be a poisonous compound having delayed action. Handle it cautiously; do not inhale it. Condensation of distilled vapors

should be done ^ith water above 10 C. to prevent

Drv ice

POISONOUS

FUMES

plugging of the condenser. Dioxane. an ether, can form

dangerous peroxides in storage. Observe the precautions

for old ether stocks in handling it.

AVOID USE WITH HANDS

Do not handle dry ice with bare hands or store it in a closed spaces. Care must be exercised in using it as

container that can be accidentally stoppered. This com- a refrigerant,

pound produces carbon dioxide concentrations in enHydrogen fluoride

EXPLOSIVE

SKIN

RRITANT

Hydrogen fluoride is extremely corrosive to the skin halation of vapors. It also generates hydrogen in contact

and lungs. It should never be used without adequate with certain .substances, creating an explosive hazard,

protection against any contact with the skin or inHydrogen peroxide

Hydrogen peroxide solutions stronger than 3 percent

call for the most careful handling. Contact with the

210627—54—2

MORE THAN 3 % = BURNS

skin may cause severe burns.
Hydrogen suifi de, hydrogen cyanide

Hydrogen sulhJe and hydrogen cynaide are dangerous

gases. They should be used only hi a well-ventilated

hood. Label cyanide solutions prominently. Do not allow

them to remain on the laboratory table except when

being used. Hydrogen sulfide is also highly flammable.

Hydrogen cyanide is moderately flammable.

Mercury

Mercury vapor is a cumulati\'e poison. Vapor pressure

of liquid mercury at room temperature is high enough

to give vapot concentrations many rimes greater than

the accepted toxic limit. Never keep mercury exposed

to the laboratory air in open containers. Clean up all

spills at once. Extreme care is necessary to collect all

the minute scatteted droplets; they evaporate slowly

and poison the atmosphere. Spilled mercury can be

CUMULATIVE

POISON

picked up with a drawn-out glass tube connected to

the vacuum line through a filter flask where the mercury is collected. Never pour mercury down sink drains;

It destroys the soldered connections. Never draw mercury into pipettes or other tubes by sucking with the

mouth. Adequate ventilation should be provided in

rooms where mercury is manipulated regularly or in

large amounts ( vacuum apparatus, gas analyses, etc. ).

Nickel carbonyl

Nickel carbonyl is an extremely toxic lung irritant

and asphyxiant with delayed action resembling that of

phosgene. Because of its slow action but high potency

and the uncertain methods of testing for it, extreme

precautions must be taken when working with this

_ LUNG IRRITANT

chemical. Experiments involving the use of nickel

carbonyl must be conducted out of doors with a favorable wind, or in a hood with positive downdraft

circulation in an isolated building.

EXPLOSIVE

Nitric acid

Nitric acid may form explosive compounds when used

to clean apparatus containing organic residues. It should

Nitriles

Nitriles, especially the lowet homologues, react in

the same way as hydrogen cyanide. Handle only under

a hood. Acrylonitrile is a very active poison; a conbe used as a cleaning agent only after careful consideration of the hazards involved.

FATAL TO INHALE

centration of 270 parts per million in the air produces

fatal results when inhaled. The maximum allowable

concentration a human being can breathe is 20 p. p. m.

Old ether stocks

Old ether stocks may prove hazardous. All ethers and

compounds containing ether linkages—acetáis, dioxane,

and furane derivatives—tend to undergo auto-oxidation

TEST BEFORE USING

in storage to form peroxides. The peroxides are relatively stable at room temperature and under dilution in

the ether, but may decompose violently when the ether
is evaporated. While any ether may form peroxides,

diethyl and diisopropyl ethers are particularly susceptible

to this oxidation. The higher boiling ethers are not so

hazardous as the lower boiling members of the series

because during evaporation the heat tends to destroy

the peroxides.

Test all old ether stocks before use. To test, shake

a small portion of the ether with aqueous potassium

iodide solution; the release of free iodine (starch test)

indicates tlie presence of peroxides. To destroy the

peroxides, add ferrous sulfate solution or sodium bisulfite until the potassium iodide test is negative. To

prevent peroxide formation in ether, store in brown

bottles or in a dark cabinet. Inhibitors, such as diphenylamine, alpiia-naphthol, hydroquinone, or metallic

copper, may be added.

Organic peroxides, peracids

Organic peroxides and peracids are capable of exploJiiig liolentl}. either spontaneously or as a result of

minute shocks, friction, or heating. Peroxides vary in

sensitivitv, but all are potentially dangerous. As far

as possible, work with these compounds should be

done on micro quantities or in dilute solution. Do not

keep them in bottles having screw tops or ground

slass stoppers. Acerjd peroxide is a dangerous explosive and, when pure, can be safely handled only behind

a barricade. It appears to be stable when in dilute solutions and should be kept well diluted at all times,

[t is advisable to prepare this peroxide in situ, or to

VIOLENT

EXPLOSION

use the commercial 30 percent solution in dimethyl

phthalate. where the phthalate can be tolerated. Benzoyl peroxide, when dry, is easily ignited and is sensitive to shock. It decomposes spontaneously at temperatures above 30 C. It is desensitized b)- adding

20 percent water. Vinylidene chloride, in the presence

of air, forms peroxides which are violently explosive.

Although phenol-type polymerization inhibitors delay

or prevent peroxide formation, storage in the absenc;

of air IS the positive method of preventing the formation of peroxides.

Perehlorates

Use perehlorates only when absolutely necessary and

only then if you are thoroughly familiar with all the

hazards involved. With dry alkyl halides, perehlorates

react to form free halogen acids and perchloric acid

in explosive quantities. Silver perchlorate crystals are

highly unstable. Although perchloric acid of 70 percent strength may be boiled safely at approximately

EXTREME HAZARD

200' C, contact of the boiling undiluted acid or hot

vapor of perchloric acid with organic matter or even

easily oxidized inorganic matter, such 'as compounds

of trivalent antimony. \\'ill lead to serious explosions.

Magnesium perchlorate sliould not be used for drying

organic materials.

Phenol

Phenol (carbolic acid) dissolved in organic solvents

is readily absorbed into the blood stream, with resulting

serious or fatal poii.o;:ing. The antidote for an accidental

KEEP

ANTIDOTE

AVAILABLE

spill is to wash all affected parts with ferric chloride in

an alcohol solution. Keep the antidote available in the

laboratory using phenol.

I

y
Pheiiyl hydrazine POISONOUS VAPORS

Fhenyl hydrazine vnpors are poisonous and may cause granular degeneration of the blood corpuscles.

Phosgene ^B

EXTREMELY DANGEROUS-DELAYED ACTION

Phosgene is very dangerous since its symptoms are

delayed 4 to 8 hours when it is inhaled in small but

toxic amounts. A lethal exposure to phosgene can

occur before any serious symptoms appear. Phosgene

IS liberated by a number of chemicals, for instance,

carbon tetrachloride.

Phosphorus

Handle phosphorus—white or yellow—with great care stored under water, it is a dangerous material to store

because it is poisonous and extremely flammable. Be- in a laboratory. It should not be allowed to come in

cause it ignites upon contact with air and must be contact with the skin.

EXPLOSIVE

Phosf)horus trichloride

Phosphorus trichloride containing moisture may form phosphine when heated, and explode violently.

Pyridine FLAMMABLE

Pyridine vapors are toxic and highly flammable

Radioactive materials V^ CONSULT

.yvK SAFETY

// \\ COMMITTEE

Radioactive materials should be used only after consultation with the Safety Committee.

Sulfonyl chlorides

HIGHLY

EXPLOSIVE

Sulfonyl chlorides are made by chlorination of mer- to explode violently during preparation,

captans and related compounds. They have been known

The following publications give further information on hazardous chemicals:

"Toxicology of Gases and Vapors," International Critical Tables, vol 2, pages .il8—321.

"Chemical Laboratories,' National Safety Council, Inc., Safe Practices Pamphlet 60, pages 11-12.

"Table of Common Hazardous Chemicals," Handbook of Fire Protection, National Fire Protection AsstKiation, 10th edition, pages .370-396.

"Controlling Chemical Hazards," U.S. Department of Labor: Series 1-4.

10
Storage and Handling

Chemicals in heavy containers should be stored on

or near the floor and in places where they are protected from colliding and falling objects.

Parts of chemical containers should not extend beyond shelving or cabinets.

Materials that react with dangerous effect should not

be stored in close proximit)- to one another, for example, oxidizing agents should not be placed near combustible materials, and strong acids should not be

stored in such a position that an undesirable reaction

can occur if the container breaks.

No chemicals m glass bottles should be stored near

a source of heat. Allow sufficient space above liquids

All bottles should be labeled distinctly and the labels

protected with transparent tape or lacquer.

Always check labels before filling bottles from stock

supply.

Identify substances in unlabeled bottles positively before use.

Test chemicals by smelling only with great caution,

by wafting a small amount of vapor with the hand

toward the nose. Avoid testing by taste.

The use of sulfuric acid or concentrated alkali solutions in gas-wash;ng bottles presents some hazard.

in bottles to take care of a considerable thermal expansion of the liquid.

Containers in which metallic sodium and potassium

are stored under kerosene or similar liquids should be

protected agamst evaporation of liquid.

Fuming nitric and sulfuric acids should be stored in

cabinets provided ^ith lead-lined trays.

Special care must be exercised to see that corrosix'e,

deliquescent, and highly reacti\e chemicals are stored

or transported in safe containers.

Special precautions are necessary- in the handling

and storage of cylinders containing compressed gases

and other cnemicals.

AWv^ check

as stoppage of the gas exit will build up pressure

which ma)' be suddenly released. Preferably, a suitable

manometric safety valve is placed in such lines.

Do not use passenger or freight elevators for the

transportation of solidified or liquefied gases, such as

carbon dioxide, ammonia, and sulfur dioxide, in Dewar

flasks or beakers. Use dumb-waiters for transporting

such materials.

Do not use sulfuric-acid baths for the determination

of melting points or boiling points. The safest practice with concentrated sulfuric acid as a desiccant is

11
CO use only enough liquid to wet some surface sucii

as glass wool or porous tile.

Do not pour or stir corrosive liquids, such as strong

acids and alkalies, witiiout proper eye protection.

Carrying materials in large glass vessels is hazardous,

especially on stairways. The safe practice is to use a

rack, canvas jacket, or other protective device. Move

the vessels on the same rit)or by means of carts or

trucks, and utilize the dumb-waiter whenever possible

to transport them to different floors. Large bottles

should not be carried by their neck.

Special teciinique is necessary in opening and handling sealed glass ampoules containing corrosive or volatile liquids. Chill the ampoule in an ice bath or in

a low-temperature refrigerator. Wrap the ampoule with

a towel, leaving the tip of the glass neck exposed;

make a scratch near the tip with a fine file or glass

knife; rest the surface of the neck opposite the scratch

on the edge of a hard support in the hood, with the

neck pointing away from the operator; knock off the

tip of the neck with a light, but sharp downward

blow. For storage of the unused portion, the ampoule

can be closed with a loose-fitting glass plug and rubber

connector, or the material can be transferred to a

small glass-stoppered bottle. Seldom, if ever, is it advisable to attempt to reseal the sample by fusing the

glass neck. This can be done safely only with materials

known to be nonflammable and nonexplosive.

Disposal

To discard small quantities of acids and alkalies,

dilute them highly with water and flush them down

the sink. Never put them in refuse containers. When

diluting a strong acid or alkali, always pour the acid

or alkali slowly into the water—never water into the

12
acid or alkali. Violent splashing may follow the pouring of water into the strong chemicals. Even putting

glassware containing unused chemicals into dishwa.shers

for cleaning has resulted in accidents to the operator.

It is the responsibility of those in charge to make certain that glassware to be washed is free from dangerous or irritating chemicals.

Collect flammable liquids not miscible with \\att:r

in tightly covered metal containers, preferably safety

cans, and pour them into an outside solvent-waste

can for disposal by burning. Never pour into the

drains or sewers. Avoid accumulation of large quantities by frequent collection and disposal. Flammable

liquids miscible with water may be poured down the

diain if dissolved in at least 20 parts of water or they

may be treated in the same manner as the nonmiscible

liquids.

Alkali-metal scrap should be placed immediately in

benzene, kerosene, or toluene. The containers should

be kept tightly closed, and the accumulated deposits

should be disposed of at frequent intervals by experienced chemists only. Small quantities of alkali-metal

residues should be disposed of by placing them in

ethyl alcohol and allowing time for complete reaction

to take place before discarding. In cleaning an alkalimetal press or other equipment which has been used

for handling alkali metal, any material adhering to the

equipment should be washed out with alcohol and

allowed to react completely with the alcohol before

discarding. AlkaH-»ietal residues shoiiid never be disposed of by reacting with water.

Alkali peroxides should be dissolved carefully by

adding a little at a time of the peroxide to a large

volume of cold watet. The solutions should be reduced

or neutralized before being discarded.

Oxidizing chemicals in general should be reduced

before being disposed of.

Dangerous chemicals, or those suspected of being

dangerous, should be disposed of only by chemists.

Cyanids and other materials capable of evolving poisonous gas should not be emptied into drains or

sewers. Disposal of such materials should be left to

the chemist in charge of the section.

Funiiaants

Fumigation is permissible only by persons specifically authorized by the Safety Committee and only

with fumigants specifically approved by the Safety

Committee.

Appropriate on-the-spot w arning signs must be posted,

and the building superintendent, the head guard on duty,

and other personnel concerned with space in which

fumigation is to take place must be yiven advance notice.

Vr,
Never put Lirge glass bottles under pressure or vacuum, unless they are protected by a shield and a

pressure- or a \acuum-limiting device.

Carry long glass tubing or apparatus \ertically, instead of horizontally, if possible.

Frozen glass stoppers and stopcocks should be taken

to a glass worker or other experienced person for

removal. Frozen rubber stoppers or corks should be

cut away from glass tubing or thermometers.

Before inserting glass tubing in rubber tubing or

in rubber or cork stoppers, tire-polish the ends of the

glass tubing or smooth them with a file and then

lubricate them with a little water, alcohol, or glycerin.

Grasp the glass tubing near the end to be inserted.

Always use toweling to protect the hands and avoid

the use of excessive pressure when inserting the tubing. This precaution is necessary when removing glass

tubing, even if not frozen. Remove rubber tubing or

stoppers that have become stuck on glassware by careful cutting with a razor blade or sharp knife, rather

than by force.

Glass tubes should always extend well through a

rubber stopper, as subsequent swelling of the rubber

might close or partially obstruct the opening.

Pick up large beakers by grasping them around the

outside, not by their rims. Filled or partly filled beakers

of large capacity should be supported on the bottom

as well as around the wall when handled.

Beakers or flasks of more than 2-liter capacity should

not be heated by direct flame or by direct contact

with a hot plate. They can break spontaneously when

liquids are heated in them and must be inspected carefully for defects before being used.

A clamp around the neck is not sufficient support

for a large flask; a bottom support is also necessary.

Inspect flasks for flaws before using them in the

distillation of flammable solvents.

Laboratory clamps of certain alloys have a low melting point and are of low tensile strength. They may

fail under a combination of high stress and only

moderately high temperature.

Do not seal off glass tubes containing combustible

materials unless the vapor pressure in the tube has

been sufficiently lowered by freezing in dry ice or a

liquid-nitrogen bath. Do not handle or open sealed

glass-reaction tubes unless they are contained in metal

protecting shells and have been adequately cooled. As

a further precaution, in opening the tubes, wear gloves

and a face shield. If you have occasion to request such

service of the glass shop, keep sealed reaction tubes

cool and within metal shells until after the pressure

has been released. The pressure may be relieved, after

cooling, by causing the tip of the tube to project

from the shell, then directing a fine flame at the tip.

Any pressure will blow out via the softened glass.

Stopcocks used in systems under slight pressure should

be held in place by rubber bands or special clamps.

Compressed air represents a hazard when improperly

used. Never dry glassware by blowing compressed air

into it. Never connect glass apparatus with the compressed-air line except through an automatic reducing

valve set at 5 pounds per square inch or less, and

protected with a safety valve or similar safety device.

14
F

Use suitable angle clamps, father than your hand

covered with a towel or rag, to hold a piece of glass

in which a hole is being cut with a power drill. If

the cutting tool sticks, the piece of glass will rotate,

unless clamped in place, with possible injury to the

operator's hand.

In sealing off solids, such as iron rods and wire, in

glass tubes, be sure that the solids have been degassed

before making the final seal. After the seal has been

made, do not heat it to a temperature higher than

that used for degassing.

In performing various operations on glass apparatus,

such as freeing frozen joints and sealing side tubes,

use a free flame only on clean, dry apparatus that has

been flushed free of flammable vapors. Before applyVacuum systeius

Glass vessels under vacuum are capable of collapsing violently, either spontaneously or from an accidental

blow. Wear goggles when working near evacuated glass

vessels. All vessels of more than 2-liter capacity should

be enclosed in a suitable shield before they are evacuated. Never evacuate ordinary soft glass bottles. Never

evacuate flat-bottomed flasks unless they are made of

heavy-walled Pyrex glass and used cold. It is a common misconception that danger of collapse exists only

with a high vacuum obtained witli an oil pump. A

low vacuum obtained with a water aspirator or the

laboratory vacuum line exerts a collapsing force fully

90 percent as great as that caused by a perfect vacuum.

The application of pressure exceeding atmospheric to

glass vessels is even more dangerous than vacuum. Never

apply positive pressures greater than 5 pounds per

square inch to glass apparatus.

Goggles or preferably a face shield should be worn

when viewing vacuum distillations and similar installations at close range. If possible, safety shields should

be placed in front of the apparatus.

Desiccators for vacuum uses should be made of

Pyrex or similar glass, and they should be protected

by standard metal screens, cages, or wooden boxes.

Dewar flasks containing liquefied gases or solid carbon dioxide must not be tightly stoppered. They must

not be placed in electric refrigerators, as these ordinarily have doors which seal airtight on closing. Dewar flasks must be closed in a wooden box or other

container or be wrapped with tape to reduce the

210527—54—S

ing the flame, satisfy yourself that the apparatus is clean

and dry.

Immediately di.scard broken beakers or other glass

apparatus in receptacles provided for such waste; do

not leave them among other glassware to be washed.

This removes the po.ssibility of cuts from washing

broken glassware.

In handling or washing laboratory watch glasses or

other fragile glassware, avoid using pressure when attempting to remove crayon identification marks or

otherwise cleaning them.

When washing microscope slides and cover slips,

take care that no broken pieces are left in the sink.

Pick up broken glassware with a broom or brush

and a dustpan, never with bare hands.

hazard of flying glass in c.ise of collapse. These flasks

are capable of collapsing as a result of thermal shock

or a very slight scratch at the neck by a stirring rod.

In general, high-\acuum distillation should be conducted with adequate shielding. They should be cooled

before venting, or vented with inert gas. Removal of

air by means of water pumps mtist be performed with

traps in the line and positive check valves to keep

water from backing up into the system.

If, for any reason, the vacuum has to be broken in

a system, the heat should also be interrupted to prevent excessive distillation rates on resumption of vacuum.

15
Pressure Reactions and

Pressure Equipment

"H '

Never connect any closed apparatus incapable of

withstanding the maximum pressure of the service Unes

—air, steam, and water—directly to the line.

Install pressure-reducing vah'e and adequate safety

release so that the pressure can never exceed that for

which the vessel is rated.

A safety valve or a metal rupture diaphtagm must

be installed where\'er the nature of the installation

would permit excessive pressures in the event that any

pressure-regulatmg device fails to function. For example, a kettle suitable for 50 pounds per square inch

should never be connected through a pressure-reducing valve to the 120-pound steam line unless there

is a safety device on the kettle. Similarly, the kettle

should not be connected even to a 10-pound line in

which the steam is obtained by reduction of 120

pounds steam unless the 10-pound line is protected

by a safety device. It is not uncommon for pressureregulating valves to stick in the open position or to

seat improperly.

A free space of 20 percent should be allowed in

a high-pressure autoclave, based on the calculated liquid

volume at reaction temperature.

Never use cooling water in the jacket of a steamheated vessel unless ( 1 ) the jacket will withstand

maximum pressure of the cooling water, ( 2 ) the drain

is open to the sewer, with no intervening valves, or

( 3 ) a safety valve is provided.

The maximum safe operating pressure should be

permanently marked on each piece of equipment.

Safety valves must have proper pressure limits and

capacity, and should be tested periodically.

All pressure equipment should be equipped with

suitable pressure gages. The range or total dial graduation should be about twice the working pressure. For

corrosive gases and liquids or viscous fluids that would

destroy a steel or bronze Bourdon tube, use a diaphragm gage. Install coil pipe or pigtail siphon before gage on steam connections.

In the design and installation of pressure equipment consult the applicable codes of the American

Society of Mechanical Engineers and the American

Petroleum Institute. Pressure vessels must pass an approved pressure test before being placed in operation.

Thereafter, they must be tested or inspected by a recognized authority at least once a year.

Pressure apparatus should not be tested with oxygen.

Systematic inspection and venting of all pressure

tubing, connecting gages, or pressure release devices

to the pressure system should be made before each

use to make sure that they are not plugged from

previous operations. Systems should be so arranged

that they may be flushed out.

Never install a pressure relief device where anyone

can stand or walk in front of the discharge.

Vessels for vacuum operation should be protected

by suitable relief valve (vacuum breaker).

Safety glasses or goggles should be worn when working with pressure reactions.

16
High-Pressure

Technique

Never hlJ a pressure vessel so full of liquid that

external heat would develop pressures in excess of the

allowable working pressure.

Never tighten a pressure joint under pressure.

Avoid even traces of oil on equipment to be exposed

to oxygen under pressure. Under strong oxidizing conditions special packing or lubricants must be provided.

Escape pipes from safety-release mechanism should

be arranged to discharge outside of building.

High-pressure reactions and equipment should be

operated only in rooms set aside for that purpose.

Highly hazardous operations should be handled from

a distance. Gages may be viewed through a system of

mirrors. Gages should be of the safety-back type.

Valves controlhng high-pressure liquids or gases

should indicate direction of flow to insure proper connection to the shut-off side of the valve with packingor stuffing-box connection on the low-pressure side.

All pressure vessels should be stamped plainly with

the maximum allowable working pressure and the maximum allowable temperature.

When working with poisonous gases, it is desirable

to have another person present. Suitable gas masks

should be used. Where more than one individual works

with pressure apparatus, the extent of individual responsibility should be clearly understood.

Pressure should be relieved and head of pressure

vessel unseated before retaining devices ( bolts, nuts,

etc.) are removed.

Damage through failure and explosion of high-pressure vessels is not confined to direct hits by parts of

the exploding bomb or autoclave and spray of autoclave contents. Secondary propelled parts are often as

dangerous as the prime movers. Special safeguards,

such as an armor-plate shield or a rope mat, should

be installed.

Pressure tubing :'i small diameter should be held

down rigidly along its entire length to prevent whipping in case of failure.

The following special precautions must be strictly

observed :

Electrical equipment, fixtures, connections, and

switches in high-pressure hydrogen laboratories should

comply with applicable National and State codes for

flammable gases.

No person, except research workers or others who

are expressly authorized, may operate or interfere with

any bomb apparatus or its accessories, gas compressor,

catalytic apparatus, or other high-pressure equipment.

When an individual engaged in high-pressure work

has reason to suspect a defect in any of the valves,

cylinders, gages, compressors, bombs, or other equipment, he must immediately have the equipment investigated and corrected if found defective.

No high-pressure experiment or operation may be

carried out or attempted unless expressly authorized

by the individual in charge, and then only under his

personal super\'ision.

No unauthorized person shall be permitted in the

room while high-pressure experiments are being prepared for or made.

The indi\idual in charge of the high-pressure work

shall be responsible for seeing that all necessary safety

precautions are observed.

For further information on this subject, consult

"Gaseous Combustion at High Pressures," by Bone,

Newitt, and Townend (Longmans, Green, and Company, Inc.).

17
Compressed Gas

Containers

Cümpressed-gcis containers are safe for the purpi)ses

for which they are intended. Serious accidents connected with their handhng, use, and storage can ahnost

invariably be traced to abtise or mishandhng.

Gas cyhnders will be tagged with metal tags in the

receiving room. On delivery, the recipient must make

certain that the cylinder is correctly tagged.

\4

All cylinders over i feet tall must be secured, by

a chain or strap on the upper part of the cylinder, or

supported by a nontipping base. Tank trucks are preferred for the transportation of cylinders, but low bases

with wheels may be used. Never move a cylinder b)'

applying force to the cylinder valve. ,

Cylinders should be protected against excessive rise

of temperature. No part of any cylinder containing

a compressed gas should ever be subjected to a temperature above 125° F., or allowed to come in contact

with a direct flame.

Never store cylinders near highly flammable substances, such as oil, gasoline, or waste, or in the direct

rays of the sun.

Do not store cylinders near elevators or gangways,

or in other places where heavy moving objects may

strike or fall on them. Avoid horizontal storage also.

Valves and safety plugs should always be protected

with a cap when cylinders are not in use or are being

transported.

Cylinder valves must be kept closed when not in use.

When opening a valve, open it slowly. Never hammer

the valve wheel in attempting to open or close the

valve.

A simple needle valve that is not completely shut

oft is capable, in time, of transmitting the full pressure

of the cylinder to apparatus connected to such a valve.

This applies also to single- and double-stage reduction

18
/^

valves that are not in working order. The proper precaution is a safet}' release valve or device in the system

to which pressure is being applied. If practicable, cylinders should be disconnected from the rest of the apparatus at the close of each day.

Accurate regulation of low rates of gas flow from a

high-pressure source should not be attempted with a

simple needle valve. A pressure-reducing valve should

be used.

Pressure-reducing valves that fit cylinders of waterpumped nitrogen or oxygen must never be used on

oil-pumped nitrogen. Oil may enter the valve, rendering

ic unsafe for future attachment to an oxygen cylinder.

Any adapters that might permit inadvertent use of these

regulators on oil-pumped nitrogen should be discarded.

Gages used on oxygen tanks are subject to explosions

of two types—simple mechanical breakage under pressure of the Bourdon tube within the gage, and actual

explosion of oxygen-oil mixtures within the gage tube.

All small gages { 3 inches or less ) used on high-pressure

oxygen should be examined for age and design, and

replaced by new safety-back gages if they are not provided with this feature. AH gages used with high-pressure oxygen should bear the following warning in a

conspicuous place: Oxygen—Use No Oil.

Each oxygen valve must bear a notice naming two

persons authorized to connect the valve. It is the responsibilitv of the safety committee of each laboratory

to see that the following precautions are posted and

observed :

1. Inspect both tank and reducing valve visually for organic matter.

2. Take all precautions for removing anv organic matter, including wiping valve with

carbon tetrachloride on a clean cloth if necessary and washing hands with soap and

water before handling valve.

3. To dislodge dust and dirt, open the tank valve momentarily before attaching the reducing valve: be sure to point the valve opening away from you. Never hammer

the tank valve.

4. Test the reducing valve by turning the tank valve on slowly, and run some oxygen

through the reducing valve. Stand so tiiat the cylinder is between your body and

the reducing valve while doing this.

For detailed information on the safe handling of compressed gases coníi.üt "Safe Handling of Compressed

Gases " Compressed Gas Manufacturers' Association.

Inc., and "Static Electricity," National Safety Council,

Inc., Pamphlet 52.

19
In the storage and handling of flammable liquids not

more than a 2-days' supply, limited to a total of 10

gallons of those that are used intermittently or only

occasionally, should be stored in any one room at any

one time. Any exceptions involving larger quantities

of flammable liquids must be approved by the safety

committee of the laboratory. All flammable liquids

should be stored in tightly sealed containers. The

liquids or their vapors should never be exposed to the

atmosphere m the presence of flame, sparks, or hot

surfaces, such as electric heating elements in operation.

As a guide to applying this restriction, a flammable

liquid shall be defined as one having a flash point

below 75° F. as determined by the closed-cup test. However, quantities of flammable liquids having a flash point

of 75° or above should be kept to a practicable minimum and should be stored in tightly sealed containers.

Safety cans should be used wherever possible for

flammable liquids.

Ordinarily, electric refrigerators are not adapted to

the storage of volatile, flammable solvents, either by

themselves or in combination with other materials,

owing to the possible ignition of the vapors by the

arcing of motor or lamp switches, or the breaking of

lamps, within the refrigerator. Unless the necessary

safety features have been incorporated in the refrigerators when purchased, all electric refrigerators shall be

properly altered or reivired promptly to eliminate these

sources of ignition, even though there is no intention

of placing flammable solvents in them.

In distilling or refluxing volatile, flammable liquids,

use a water or steam bath rather than a free flame or

a hot plate. Heating mantles or similar systems are also

advantageous. Where practical, conduct all distillations

in a hood. Pay careful attention to operation of the

heating appliance at the proper temperature and to

adequate cooling of the condenser. Set up the flask in

an empty container, or in a tray containing sand, capable

of confining all of the liquid in case the vessel fails.

Distillation equipment in operation should not be left

unattended.

Vacuum distillations in flasks of more than 500

miUiliters should be carried out behind a safety shield or

safety glass to protect not only the operator but also

others in the vicinity in case the flask collapses. Goggles

protect only the wearer.
No open Hames should be allowed where flammable

gases, vapors, or dusts are present. Gases or vapors

heavier than air will seek the lowest level and may

float along bench and table tops or the floor for considerable distances. Sources of ignition many feet away,

therefore, may cause an explosion or fire. Conspicuous

signs warning against smoking and the use of open

flames should be displayed prominently.

Use liquid nitrogen in place of liquid air as a refrigerant for cooling flammable liquids in glass vessels.

Do not keep even small bottles of volatile, flammable

liquids in the sunshine or where heat from a hot plate,

burner, or other device may cause the stopper to blow

out and release vapors.

Flame arresters should be installed in vent or vacuum

lines connected to processing equipment containing

flammable liquids.

Safety valves must always be vented to the outside

if there is a possibility of their discharging flammable

gases or liquids.

Gage-glass valves should be of the automatic selfclosing type.

Electrical wiring and apparatus for use in hazardous

places should be of the type approved for such places.

(See "Hazardous Locations," Article 500 of the National

Electrical Code. )

Be sure that no electrical apparatus employing a

device which may produce sparks, such as an open

relay, is operated where flammable vapors are present.

Electric refrigerators equipped with outside relays are

typical examples.

The electric breaker switch with which some motors

are provided may also be a source of ignition of

flammable vapors. Motors so equipped should not be

operated where such vapors are present. For stirring

volatile solvents use explosionproof electric motors or

motors operated with air or water under pressure.

Where flammable gases, vapors, or dusts may be

present, use nonsparking tools. Power transmission for

equipment should be of the type that will not produce

sparking or build up electrostatic charges.

The exposed, noncurrent-carrying metal parts of

equipment used in hazardous locations should be grounded in accordance with the requirements of article 250

of the National Electrical Code.

Where unstable substances capable of exploding are

dried in electric ovens, all rigid door latches should be

removed and the oven surrounded by a suitable protective cage. However, solids containing even small

amounts of volatile, flammable liquids should not be

dried in electric ovens with exposed heating coils or

switch contacts.

Do not solder or use open flames on pipes or vessels

that have contained flammable materials unless all of

the flammable material has been removed and the pipes

or vessels have been cleaned thoroughly. If possible,

have them filled with water while the work is being

performed.

Provide exhaust systems to remove fumes and dusts.

Where flammable gases may be present, use steam

instead of compressed air to clean machinery.

Valves and pipes carrying flammable materials should

be prominently identified. (See "Identification of Piping

Systems," National Safety Council, Inc., Safe Practices

Pamphlet 88. )

Oily rags or waste should be placed in metal containers with close-fitting covers. Containers must be

emptied and contents properly disposed of at the end

of each day.

For detailed information on the fire-hazard properties

of flammable liquids, gases, and volatile solids, consult

"Handbook of Fire Protection," National Fire Protection Association, 10th edition, pages 233-.^01.

21
Electrical Installations

v.

Fluorescent lamps containing beryllium compounds

present a poison hazard when broken. Poisoning may

result from inhalation of the materials; introduction of

the powder into cuts or breaks in the skin causes sores

which are diiïicult to heal. Great care must be taken,

therefore, in handling and disposing of broken or burnedout lamps. If a fluorescent lamp breaks while in use,

avoid inhaling the air in the space where the breakage

occurred until the area has been properly cleared of

powder and broken glass. Burned-out lamps should be

replaced only by the electrical shop. An individual shall

be designated to arrange for the proper disposal of

burned-out and broken lamps.

Electrical wiring and equipment for use in hazardous

locations should comply with the requirements of

Article 500 of the National Electrical Code. ( It is suggested that the electrician be consulted before ordering

electrical equipment. )

All electrical alterations and repairs should be made

by the electrical shop. In case of necessity, however,

qualified laboratory workers may perform minor electrical jobs, provided they are authorized to do so and

such work is inspected by the electrical shop.

Temporary electrical installations which may be necessary to expedite important research should be made

only by an electrician. If it is found later that electrical

service is required for an extended period, the temporary

installations should be replaced by approved fixtures and

appliances as soon as possible. Temporary installations

definitely made for a short period should be dismantled

and discarded just as soon as the need for them has

passed.

For the protection of personnel, the work areas, such

as laboratory benches and hoods, are served by a threewire electrical distribution system, the third wire of

which provides a protective ground. All equipment

served by these outlets should utilize this safety feature.

Keep the use of extension cords at a minimum. Such

cords should be of the approved type and as short as

possible, and they should not be used as substitutes

for permanent or fixed wiring.

Take care not to overload electric motors, Variacs,

and Variatrans.

Before plugging in electrical equipment, be sure that

switches on the equipment are turned ofï.

22
Do not fasten or block the throw of circuit breakers.

Check the demand on workbench and hood circuits

before adding any large load.

Flush-type door receptacles, when not in use, should

have the removable screw top properly inserted.

Adequate precautions must be taken with high-voltage

equipment. A conspicuous sign showing operating voltage should also be displayed.

A cutoff switch in the input to high-voltage and

machinery circuits should be provided and used.

Process equipment

Gage-glass valves should ordinarily be of the automatic, self-closing type.

Keep hands out of moving conveyors. Means for

feeding machines must not endanger the limbs of operators.

Operators around moving machinery should not wear

loose neckties, clothing, and coveralls. Women operators

should wear hair nets or caps.

Where practical, use color codes and prominent labels

on all pipe lines.

Do not lubricate shafting or machinery while in

operation.

Do not enter tanks without providing a fresh air

supply; also have another person nearby to aid in case

of an emergency.

Do not enter a large tank or vessel equipped with

an agitator unless the mam switch is open and another

person is near to prevent starting of the agitator.

If jackets or coils are arranged for alternate steamheating and water-cooling, constant care is necessary to

avoid entry of untreated water into the condensate

return lines. A warning sign should be installed.

In pr(jcessing vessels heated by diiect admission of

steam, condensate must be run into the sewer—never

into the condensate return lines.

Never open or close any valve or switch witliout

informing all users of the service.

Do not take the word of the previous operator that

all valves, pumps, etc. are properly adjusted; check them

yourself. Do not leave your shift without thoroughly

acquainting your successor with all of the unusual conditions that prevail.

Avoid the use of three-way valves if two ordinary

valves will serve the purpose. Three-way valves often

cause confusion and may be turned the wrong way in

an emergency.

Automatic valves, which will shut off fuel burners

when the supply fails, must be provided.

Steam pipes and other hot lines near working levels

must be insulated to prevent burns.

Pressure must be removed from pipe lines and vessels

before repairs or alterations are made.

210.527—Ó-1—4
Miscellaneous laboratory and

pilot-plant technique

Ball-mill grinding is hazardous if iron balls are used

in the presence of aqueous liquids because appreciable

hydrogen pressure may develop.

Before a centrifuge is operated for the first time, be

careful to follow the manufacturer's instructions and

to properly secure the basket or head in position. When

a centrifuge is provided with a housing having a lid, it

should not be operated with the lid open or unlocked.

A centrifuge that does not have a protective, stationary

housing should not be used without a suitable safeguard

to protect the operator. The speed limit recommended

by the manufacnirer must not be exceeded.

Persons working near an agitator containing corrosive

substances should wear a face shield.

Guard against sudden vaporization of liquid because

of superheating. Never add a boiling stone or similar

device to liquid after heating has begun.

Bottles or other containers made of flint or soda-lime

glass cannot be heated or chilled rapidly without cracking or breaking. Only Pyrex or similar glassware should

be used under such conditions.

Be sure that condenser water has been turned on

and remains turned on when using volatile, flammable

solvents in Abderhalden dryers and distillation apparatus. Make certain that the cooling water is at a sufficiently low temperature.

^m//

24
Never conduct operations over a grating, if spilled

material could cause injury to someone below.

A wet place on the floor may be the result of an

overhead spill; therefore, do not look directly upward.

Drink from drinking fountains rather than from

beakers or other laboratory utensils.

Pipette and siphon poisonous or corrosive liquids bv

means of mechanical suction, not by the mouth.

The use of individual wash bottles or bottles equipped

with rubber bulbs prevents the spread of colds or other

infections.

Do not stand on boxes or swivel stools to work. Use

suitable ladders or platforms.

Exposed, noncurrent-carrying metal parts or fixed

and portable equipment, which may become electrically

energized, should be grounded m accordance with the

requirements of article 250. "Grounding." of the National Electrical Code.

Charges of static electricity may he generated hy bringing together and

separating two substances, one or both of ichich are nonconductive. Static may

also be generated by the separation of a vapor or liquid into particles. Ex-

^^ j amples are steam leaking from a pipe, or a stream of liquid breaking up into

y drops, as happens in the pumping of liquid into a tank from above (even tcithin a closed system).

If the static charges build up to a high enough voltage, they jump across

gaps, forming sparks ivhich may ignite flammable gases, vapors, or dusts.

One common hazard results from the transfer of a nonconductive liquid

from one container to another. This can be controlled by connecting electrically the container and receiver, and grounding the system.

Another hazard may result from the operation of blower systems handling

dusts.

\f henever flamtnable materials are involved, consider possible sources of

static generation, and eliminate any hazard by careful grounding.

For more detailed information, consult "Static Electricity.'' National Safety

Council, Inc.. Safe Practices Pamphlet 52: and MFPA .Vo. 77 "Static Electricity." National Fire Protection Assoc. Boston. Mass.

Provide handrails on stairs and platforms. Have platforms above shoulder

height equiped with toeboards.

Illumination should be adequate everywhere.

^^^

f r^ A o /-> 1 Report escaping gas to your supervisor if its source cannot readily be deter-

—'— -^^ mined. L'nsafe conditions, operations, or equipment should also be reported to

liini.

All gas burners, ivith the exception of glassblower's burners. Bunsen, and

Meker laboratory-type burners, must comply with one of the following conditions: (1) The burner must be connected to the gas supply ivith rigid metal

piping; (2) ivhere rubber tubing is used for conveying the gas, the stopcock

on the burner must be fixed in an open position or removed entirely so that

it cannot be used to shut off the gas and leave the rubber tubing holding gas

under pressure.

In the case of the burners that are excluded from this

requirement, the gas must always be turned off at the

bench outlet.

No apparatus. J?¡ng heat, which presents a fire or

explosion hazard because of the possibility of overheating, or of accidental ignition of flammable materials

bv the heating medium, shall be operated at night or

(n'er the week end without an attendant.

25
Mechanical and shop equipment

General precautions

No person should operate any machine in the mechanical shops or elsewhere without permission of his

supervisor and the man in charge of the machine.

Interrupting a workman who is busy on a power-driven

machine, such as a lathe, drill, milling machine, or pipethreading machine, may cause him to have an accident.

The safe thing to do is to wait until he is free or to

see his supervisor.

While only one starting button should be provided

for each machine, several auxiliary or safety stops may

be advisable so that the machine can be conveniently

shut down by fellow workers in case of accident to the

operator.

% '^^

Where possible, safeguards should be provided for each point of operation to prevent

injury to the operator from dangerous moving parts or from the moving material. This may

be accomplished by using one or more of the following devices:

Mechanical feeding device.

Hand-control device at a safe distance from the point of operation.

Tool so designed that it is impossible for the operator to get in the danger zone.

Device that interrupts the movement of the tool or machine while any part of operator's body is in the danger zone.

Device that pulls or pushes the operator's hands away from the danger zone.

Barricade, cover, guard, or enclosure.

Never allow a machine to run unattended. Shut ofiF the power immediately after finishng a job. Someone else may be injured by a machine that is running when he has reason

to think it is not.

Never use the hands or feet for braking machines.

Operators of machines in which clothing may become entangled should wear snugfitting, short-sleeved shirts or jackets and no neckties. Neckties offer a serious hazard, as do

rings and wrist watches. Gloves should not be worn.

Floors should be kept in good condition and free

from chips or obstructions. Slippery floors around machijies are especially hazardous.

Exhaust systems should be provided for collecting

vapors, fumes, and objectional dusts at their sources

and discharging them outside the building.

Spray painting should be done only in properly

designed spray booths, preferably of the water type, or

in large spaces, well ventilated.

Exposed belts and pulleys, gears, projecting parts,

shaft ends, clutches, and other moving parts present

definite accident hazards. Suitable guards should be

provided; they can be designed and applied best by

the machine builder.

26
Chip guards (shields) should be available for use

on lathes, shapers, and other machines when needed.

Also, goggles should be worn when needed. The shields

are particularly desirable when brass, cast iron, or tool

steel is being machined because chips are most likely

to fly from these metals.

Fluorescent lighting can produce a stroboscopic effect

on rapidly revolving parts of machinery, thus giving

a false impression of true speed. Allow for this effect

and take precautions to prevent accidents from it.

Specific machines and equipment

Lathes

Safet}' lathe dogs, such as those having countersunk setscrews. rather than lathe dogs with protruding setscrews, should be used.

Whenever chucks or faceplates are changed, they should be started on the spindle by hand power, never

by machine power.

See that the work is counterbored to sufficient depth to prevent its being torn loose.

Be sure that the lathe spindle fits its bearings and that the carriage is not loose on the ways.

Do not attempt to change or adjust machine tools while the lathe is in motion.

Pipe guards should be installed to prevent a fellow worker from being caught on the projecting revolving stock.

Drill presses

Never attempt to hold the work by hand when using the drill. Make it secure with a clamp.

Avoid forcing or feeding the drill too fast. Broken or splintered drills have caused serious injuries.

Never use the fingers, cotton waste, or rags to brush chips away from the drill; use a stick or brush.

Never use gloves in operating a drill press except when handling rough materials and then only when the

drill is not running.

Keep your hair away from the drill or drill spindle. Wear a cap or keep your hair cut short.

Be careful how you reach around the levolving drill. Keep your sleeves short or they may catch on it.

Milling niai-hines

When setnrit; up jobs or making adjustments, never fail to stop the cutting tools.

Make sure t^-it cutter and arbor are secure.

27
See that the work is clamped securely.

Avoid cuts and other possible injuries by using a brush to remove chips.

Be careful about your clothing; loose garments are easily caught in machinery.

Keep the floor around the machine clean and free from objects that might cause a fall.

Hacksaws (Power)

Hacksaws should be so placed that the end of the material being cut does not protrude into a passageway.

Be sure that the material is clamped securely and that the piece being cut ofif will not fall where it may

injure someone.

Abrasive wheels

Abrasive wheels are fragile and present exceptional hazards if abused either in handling or in operation.

Breaking of the wheel and accidental contact with the wheel while it is in motion are the principal causes of

injuries.

See that wheels are properly mounted and equipped with suitable guards. All wheels should be given the

"ring" test before rhey are mounted. After a wheel has been mounted, it should be allowed to develop its rated

operating speed for at least one minute, during which time the operator should stand aside and out of danger.

Never operate wheels above normal or specified speed. Do not use wheels having uneven or rough surfaces or

wheels that make the machine vibrate, indicating that they are out of balance. Have rough wheels dressed by

someone who knows how.

The operator should wear goggles.

When using sanders, wear goggles, and be sure that the work is held securely in place on the bed. Do not

try to sand pieces that are too small to be handled safely. Be especially careful when sanding round pieces.

Welding (Oxy-acetylene and electric arc)

Only properly trained and instructed persons should operate welding apparatus.

Operator should wear a mask protecting eyes and face and suitable clothing for protecting the body from

rays of arc or flame and against hot metal sparks.

When welding or cutting, use proper equipment, shields, booths, sheet-metal guards, asbestos paper or curtains to protect other persons from the arc rays and to keep flames, sparks, molten slag, and hot metal from

coming in contact with combustible material.

Welding or cutting must never be permitted near explosive gases or flammable liquids, regardless of the precautions taken.

28
Before welding or cutting in a new location for the first time, check with the foreman or person m authoi-

^ ity for possible serious explosion or fire hazard.

feasible, move work to a location where there is no possibility of setting fires.

Kemove combustible materials to a safe distance, if possible. Use noncombustible material for supporting

work.

öefore starting welding or cutting operations on a pipe or vessel which has, or may have, contained flammable

materials, be sure that the container is free from explosive vapors. If possible, purge it with steam or an inert

gas, or nil it with water while work is being done. Never work on a container that may be sealed or plugged

so that the expanding gases cannot escape.

Keep a dry-chemical, or carbon-dioxide, fire extinguisher handy, if possibility of fire exists. On maintenance

of carbon-dioxide fire extinguishers consult National Board of Fire Underwriters Pamphlet 10.

Areas in which cutting or welding is being done should be well ventilated.

Wear clear glass goggles when hammering or chipping scale.

For arc welding when changing electrodes, the operator must be kept insulated from the ground and metal

objects nearby. Make welding connections direct to the ground whenever possible. When connecting to metal

structures, make sure a fire cannot be caused at some distant point. Warning signs or other means should be

used to keep people away from power lines to welding machine.

Use only hose made especially for oxy-acetylene welding and cutting. Do not use metal-co\ered hose. Use only

standard hose connections in connecting hose to blowpipes and regulators.

Use regulators or automatic reducing valves only with the gas for ^hich they are intended.

Do not store extra gas cylinders within the working area or in the direct rays of the sun.

For information on the safe handling of oxygen and acetylene cylinders, see "Safe Handling of Compressed

Gases," Compressed Gas Manufacturers' Association, Inc., bulletin.

Compressed air

Many hazards arise from improperly installing, maintaining, and operating compressed-air equipment. Fatal

accidents or serious injuries may result from explosions in air compressors and receivers, and also from the introduction of compressed air into the eyes, ears, or other openings of the body. Compressed air, when misused, can

be extremely dangerous. Under no circumstances should a worker aim an air hose at anyone. Air under presstire

will pass through clothing, and serious injury is possible. Its use for cleaning clothing, therefore, should be energetically discouraged.

For information on this subject, see "Compressed Air Machinery and Equipment," National Safety Council,

Inc., Safe Practices Pamphlet 47.

Jointers

Be sure that the cutters are in good condition, sharpened, and securely held on the arbor.

Do not use jointer on pieces of wood less than 12 inches long.

When working on plywood, joint only the edges.

29
Power saws (baiul, bench, and swing)

Be sure that the saw is not defective and that it is firmly held in place and operated at the proper speed.

Saws should be equipped with proper guards and with "kick-back dogs." . ,

Material should be held firmly against the gage while being sawed, with the hands at a safe distance from the

saw Be sure the material contains no nails. , , t

When short pieces are sawed, do not feed the stock with the fingers. Use a stick of hard wood made for

the purpose.

Never place the hands back of the saw or pull the work through from the back.

When using the ripsaw, do not try to rip a piece that is too narrow.

Do not allow wood scrap to accumulate on the machine bed.

Before attempting to change saws or work on machine in any way, be sure to pull disconnecting switch on

starter. Do not rely on the push-button control.

Care of Machines

All machinery should be kept in repair. Failure of

a machine to run properly should be reported immediately to the foreman. Repairs or adjustments should

not be made while machinery is in operation. The

repairman should make sure that power cannot be

turned on without his knowledge and permission.

All machines should be cleaned and oiled and their

condition checked at regular intervals. Machinery should

not be lubricated while in operation.

Care of Tools

The use of tools of poor quality or in poor condition

is hazardous. Never use a tool with a faulty handle

or a cold chisel, chisel bar, or cutter, or a tool with a

mushroomed head. Such heads can readily be corrected

by grinding.

Keep the jaws of all wrenches in good condition,

and caution workers against misusing them.

Keep sharp-edged tools sharp. This will eliminate

strains and slips. The edges should be protected while

the tools are in storage.

Portable electric tools and pneumatic tools should

be kept in perfect working condition. Special attention

should be given to the cable and hose connections and

to the control valves and switches.

30
^

Handling equipment and material

The hoisting and moving of heavy equipment muse

be supervised by a qualified individual. The lack of

proper supervision or the presence of too many bosses

may cause a serious accident.

The use of cranes must be restricted to designated

individuals who are fully qualified to operate them

and who will be responsible for their proper use. One

of the chief dangers of using cranes is failure to properly secure the load to be moved. When a large

traveling crane is not in use, the central chain must

be secured to a vertical column and the lifting assembly must be left at least 8 feet above the floor. No

one should be permitted to ride on the load or the

hook.

When installing heavy apparatus, make ample provision for future dismantling when repairs will be

required. Provide lifting hooks and supports for heavy

parts that must be removed. Before installing or hoisting heavy equipment, consult the building superintendent as to possible overloading of floors or structural members.

Do not 0%'erload chain falls, blocks and tackles, or

ropes. Know the load limits.

Do not stand beneath loads being lifted.

Limit loads lifted by hand and learn to lift the

right way to avoid body strain. Bend your knees; keep

your body erect; keep your mouth open; then push

upward evenly and gradiicdly with your leg muscles.

Do not use a ladder that is defective or insecurely

supported. When a ladder is placed in position, the

horizontal distance from the top support to the foot

of the ladder should be about one-fourth the length

of the ladder. Ladders for use on smooth surfaces should

be equipped with safety shoes. Only one person should

be on a ladder at one time. Ladders must not be placed

in front of doors opening toward them unless the d(X)rs

are blocked open, locked, or guarded.

Sharp edges and burrs on iron and steel stocks and

splintered edges of lumber stocks may cause painful

scratches and cuts. The use of hand-leathers and gloves

in handling material will prevent many injuries of this

nature.

When material is heavy or bulky, obtain help in

handling or moving it. Select one individual to superase or direct operations and abide by his instructions.

Metal and lumber stocks should be kept in racks

pro\-ided for that purpose. They should not be allowed

to lie scattered on the floor or to project into aisles

or passageways, where they may cause injury.

See also "Machine Shops," National Safety Council,

Inc., Safe Practices Pamphlet 39.

Housekeeping

Keep the plant clean; allow no trash or dust to accumulate.

Supply receptacles for waste materials. Place oily

raas and other combustible wastes in metal containers

with close-httm;-' covers.

Keep passagev, avs and exits clear of obstructions.

Leave no lumber with protruding nails on the floor.

210.5ÍT—54—5

Pick up all discarded material.

Never leave tools on a ladder or stairway.

Provide guards for openings in the floor, such as

those caused by temporary removal of gratings and

drain covers.

Do not leave broken glass in towels.

31
Office and miscellaneous hazards

Falls may occur in all types of work, but they can

easily be prevented. One of the most common causes

IS undue haste on a slippery floor or running up and

down stairs or in corridors. Floors should not be highly

polished. Spilled liquids should be removed promptly.

Traffic avenues should be kept free of equipment or

material which constitutes a tripping or obstruction

hazard. Standing on chairs and stools or tilting chairs

while sitting in them should be avoided.

Not more than one drawer of a filing cabinet should

be pulled out at any one time. Two heavily loaded

upper drawers opened at the same time may make

the cabinet so top-heavy that it overturns. Desk and

filing cabinet drawers should not be left standing open.

Stiff paper, if not handled carefully, may cause serious cuts.

Do not discard cigarette and cigar stubs, pipe ashes,

and matches in waste-paper baskets; use ash trays.

Do not throw broken glass or other sharp objects

into waste-paper baskets.

There is a collision hazard at every blind corner.

Corridors should be well lighted.

Protective equipment for personnel

Employees handlmg acids or other corrosi\e substances should wear rubber gloves, chemical workers

goggles or face shields, and aprons.

Goggles or face shields should also be worn by other

employees engaged in work which may result in injury

to the eyes. Goggles of the proper type should be used

for the particular hazard involved, such as impact, dust,

splash, glare, or injurious light rays.

Fitted or prescription spectacle goggles are furnished

to all employees who work in areas designated as hazardous. They must be worn at all times in these areas for

general work. For specified hazardous operations additional protection is required, as indicated in various

places in this manual.

Safety shields constructed of shatterproof glass or

heavy wire screening should be placed around all equipment where there is a possibility of rupture or shattering of the apparatus. These enclosures should be used

e\en thout;h the operator is wearing goggles or a face

shield; there is alwavs the chance that persons working

.near him. and not so protected, will be injured.

Employees whose duties bring or may bring them

in contact with an atmosphere deficient in oxygen or

with poisonous or irritating gases, fumes, vapors, or

dusts should wear respirators, gas masks, or other protective breathing equipment approved by the United

States Bureau of Mines. A gas mask is not protection

against an atmosphere deficient in oxygen. In such

situati()ns, ventilation or a hose mask having an air or

Mxygen supply is required. (See p. 3.)

Protective equipment should be readily available and

should be maintained properly. Emplovees should be

trained in its proper use.

Adequate warning signs should be displayed prominently to indicate the nature of the precautions neces-

'•arv around hazardous work.

32
Appendix

The following míormation is taken from "General

Industry Safety Orders, " Division of Industry Safety,

Department of Industrial Relations, San Francisco,

Calif.

Concentrations of various substances in which it is

considered safe for men to wotk, whether for brief

periods or for full working periods daily for an indefinite time, are given in tables 1 to 4. Most of the

figures are tentative and subject to revision in the light

of further research and experience. Even for those

which are best established, differences of opinion are

found among authorities. The figures are given as an

indication of current opinion and practice, doubts being resolved on the side of safety.

It cannot be taken for granted that concentrations

higher than those given in the table are safe for short

and occasional exposure. There is no readily calculable

relation between the effects of short, heavy exposures

and long, light exposures. It cannot be assumed that a

substance safe for 8 hours in a concentration of TOO

parts per million will be safe for 1 hour at 800 parts

per million; still less at 8,000 parts per million for 6

minutes. Neither can it be assumed that, because two

substances are tolerable in the same concentration for

long, light exposures, their action will be the same for

short, heavy exposures, or vice versa.

The absence of a substance from the tables does not

necessarily mean that it is less toxic than some of the

substances listed. Many substances which it would have

been desirable to include have been omitted for lack

of data.

It is not implied that because two substances have

the same or nearly the same maximum acceptable concentrations, the hazards connected with their use are

necessarily of the same order of severity. In some

cases, maximum acceptable concentrations are set up

with a view to preventing systematic damage, and

exceeding such concentrations may result in severe injury. In other cases, maximum acceptable concentrations are set up with a view to avoiding relatively

slight, though still harmful, effects, such as dizziness

or irritations of eyes, nose, or throat.

Substances which ha\-e the same maximum acceptable concentration expressed in parts per million do

not necessarily present an equal hazard on a weightfor-v.'eight basis. Other things being equal, the weight

of a given volume of vapor is a function of the molecular weight of the substance, and a stated concentration in parts per million may represent for one

substance se\eral times the weight of the same concentration of another substance.

Table I. — Mineral Dusts

Milli':ii particle

per cubic foot

Total düst . 50

Asbestos 5

Silica (free or uncombined)

Less than 3 percent 50

5 percent to 25 percent 20

25 to 50 percent 10

Over 50 percent 5

Talc ( commercial or industrial; 20

Talc (chemically pure steatite; 50

NOTE. The maximum acceptable concentrations for dusts in this Appendix contemplate

the estimate of dust exposures bv the method recognized by the U.S. Public Health Service.

?3
Table II. — Metallic Dusts, Fumes and Vapors

Milligrams

per cubic

meter

Antimony 0.5

Arsenic and compounds ( except volatile hydrides ) 0.5

Barium 0.5

Cadmium 0.1

Chromium, chromic acid and chromâtes (as CrO:i) 0.1

Lead 0.15

Manganese 6.0

Mercury 0.1

Selenium 0.1

Tellurium 0.1

Zinc oxide 15.0

Total metal fumes 30-0

Table III. — Miscellaneous Dusts. Fumes and Mists

.Willigrams

per cubic

meter

Chlorinated diphenyls 1.0

Chlorinated diphenyl oxide 1.0

Chlorinated naphthalenes:

Tri- and mixtures of tri- and tetra- 5.0

Tetra-, penta- and mixtures of terra- and penta- 1.0

Hexa- and mixtures of penta- and hexa- 0.5

Fluorides 2 5

Tetryl, TNT, DNT 15

Table 1 \ . — Gases and Vapors

Parts per

million

Aceraldehyde ^ 200

Acetic Acid , (^

Acetic Anhydride c

Acetone <-„„

Acetylene tetrachloride—See 1, 1, 2, 2-Tetrachloroethanc'.

Acrolein . _

Acrylonitrile ^„

Allyl alcohol

AUyl chloride ' ' '^ ' '^ '^ '^ '\^^^^^. '^ '\ 5O

Ammonia

Amvl acetate

, , , ^ , 200 Iso-amyl alcohol

, ... 100 Aniline

Arsine

Benzene ( benzol ) ^ ' ^ï ' '^'^'^

Benzine ( gasoline )

Bromine ' ^ '' ^ ' ^ ^ ! ^ !!!!!'' ^ T '' ' ^^'^

1, 3-Butadiene

n-Butanol ( butyl alcohol ) '.'.'. ' ''"^'^'

2-Butanone

n-Butyl acetate '

Carbon dioxide - "

Carbon disulhde ^ . .Ï . ^ . .Ï . ^ '^'^^^

Carbon monoxide

Carbon tetrachloride "^"^

Chlorine • 50

1

34
Table IV, — Gases and Vapors (Coiiunued)

Parts pef

'million

Chlorobenrene 75

2-Chlorobutadiene (chloroprene) -^

Chloroform 100

1-Chloro-l-nitropropane ^^

Chlorophenols * 5

Cresol 5

Cyanogen and compounds as CN t 20

Cydohexane ^00

Cyclohexanol 100

Cydohexanone 100

Cyclohexene 400

o-Dichlorobenzene 50

1, 1-Dichloroethane (ethylidene dichloride) 100

1, 2-Dichloroechane ( ethylene dichloride ) ~5

1, 2-Dichloroethylene 200

Dichloroethyl ether 15

Dichloromethane 500

Dimethylaniline 5

Dimethyl sulfate 1

Dioxane 100

Ethyl acetate 400

Ethyl alcohol 1,000

Ethyl benzene 200

Ethyl bromide 200

Ethyl chloride 1,000

Ethylene chlorohydrin 5

Ethylene dichloride. See 1, 2-dichloroethane.

Ethylene oxide 100

Ethyl ether 400

Ethyl formate 100

Ethylidene dichloride. See 1. 1-dichloroethane.

Ethyl methacrylate 400

Ethyl silicate 100

Formaldehyde 5

Gasoline 1,000

Glycol ethers:

Diethylene glycol monoethyl ether (carbitol ) 200

Ethylene glycol monoethyl ether (cellosolve) 200

Ethylene glycol monoethyl ether acetate ( cellosolve acetate ) 100

Ethylene glycol monomethyl ether ( methyl cellosolve ) 25

Ethylene glycol monomethyl ether acetate (methyl cellosolve acetate) 25

Ethylene glycol monobutyl ether ( butyl cellosolve ) 200

Heptane 1,000

Hexane 1.000

Hexanone. See methyl butanone.

Hexone. .See methyl iso-butanone.

Hydrogen chloride ( hydrochloric acid ; 5

Hydrogen cyanide ( hydrocyanic acid) 10

Hydrogen fluoride ( hydrofluoric acid ) 3

Hydrogen selenide 0.05

Hydrogen sullide -"

Iodine

TT

Isophorone

Mesityl oxide

Methanol (methy! .ilcohol; 200

See footnotes ¡.c f ñJ of table.

.i5
Table IV. — Gases and Vapors (Continued)

Parts per

million

Methyl iicet.ue 200

Methyl bromide ^-"

Methyl butanone 100

Methyl chloride 100

Methyl cyclohexane 500

Methyl cyclohexanol 100

Methyl cyclohexanone 100

Methvl ethvl ketone. See 2-butanone.

Methyl formate , . 100

Methyl iso-butyl ketone 100

Methyl methacrylate 500

Méthylène dichloride. See dichloromethane.

Monochlorobenzene. See chlorobenzene.

Mononitrotoluene . 5

Naphtha, coal tar 100-200

Naphtha, petroleum 1,000

Nitrobenzene 1

Nitroethane 100

Nitrogen oxides—NOi' 25

Nitroglycerine 0.5

Nitromethane 100

2-Nitropropane 50

Octane 1 000

Ozone I

Penwne 1^000

Pentanone ( methyl propanone ) 200

Phenol 5

Phosgene 1

Phosphine Q QJ

Phosphorus trichloride 0 5

Iso-propanol ( iso-propyl alcohol) 400

Propyl acetate 9QQ

Iso-propyl ether JQQ

Stibine Q j

Stoddard solvent 1 QQQ

Styrene monomer

Sulfur chloride

Sulfur dioxide

Sulfur trioxide

1, 1, 2, 2-Tetrachloroethane c

Tetrachloroethylene 1 QQ

Toluene (toluol)

Toluidine

Trichloroethane '

Trichloroethylene

Turpentine

Vinyl chloride . CQQ

Vinyl cyanide. See acrylonitrile.

Xylene ( xylol )

Xylidine. See dimethylaniline.

200

1

10

10

200

5

50

100

100

200

*For nionochlorophenol. The mg-per-cubic meter values for other chlorophenols depend on

their molecular weights.

tFor cyanogen, C2N2. The mg-per-cubic meter values for cyanogen compounds depend on

their molecular weight.

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