May 1994

Documentation for Immediately Dangerous To Life or Health 

Concentrations (IDLHs)

Introduction

The immediately dangerous to life or health (IDLH) values used by the National Institute for 

Occupational Safety and Health (NIOSH) as respirator selection criteria were first developed in 

the mid-1970's. The Documentation for Immediately Dangerous to Life or Health (IDLH) 

Concentrations is a compilation of the rationale and sources of information used by NIOSH 

during the original determination of 387 IDLH values. In addition, NIOSH continues to 

review, document, and revise the science and methodology behind the existing IDLH values 

when appropriate, and derive new IDLH values.

Background

The concept of using respirators to protect workers in situations that are IDLH was discussed 

at least as early as the 1940's. The following is from a U.S. Department of Labor bulletin:

The situations for which respiratory protection is required may be designated as, (1) 

nonemergency and (2) emergency. Nonemergency situations are the more or less normal ones 

that involve exposure to atmospheres that are not immediately dangerous to health and life, 

but will produce marked discomfort, sickness, permanent harm, or death after a prolonged 

exposure or with repeated exposure. Emergency situations are those that involve actual or 

potential exposure to atmospheres that are immediately harmful and dangerous to health or 

life after comparatively short exposures. [Yant 1944] 

The Occupational Safety and Health Administration (OSHA) defines an IDLH value in their 

hazardous waste operations and emergency response regulation as follows: 

An atmospheric concentration of any toxic, corrosive or asphyxiant substance that poses an 

immediate threat to life or would cause irreversible or delayed adverse health effects or would 

interfere with an individual's ability to escape from a dangerous atmosphere. [29 CFR* 

1910.120] 

In the OSHA regulation on permit-required confined spaces, an IDLH condition is defined as 

follows: 

Any condition that poses an immediate or delayed threat to life or that would cause irreversible 

adverse health effects or that would interfere with an individual's ability to escape unaided 

from a permit space. Note: Some materials--hydrogen fluoride gas and cadmium vapor, for 

example--may produce immediate transient effects that, even if severe, may pass without 

medical attention, but are followed by sudden, possibly fatal collapse 12-72 hours after 

exposure. The victim "feels normal" from recovery from transient effects until collapse. Such 

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materials in hazardous quantities are considered to be "immediately dangerous to life or 

health." [29 CFR 1910.146] 

As part of their current respiratory protection standard [29 CFR 1910.134(e)], OSHA requires 

that a standby person be present with suitable rescue equipment when self-contained 

breathing apparatus or hose masks with blowers are used in atmospheres immediately 

dangerous to life or health. Furthermore, persons using air-line respirators in atmospheres 

immediately hazardous to life or health must be equipped with safety harnesses and safety 

lines for lifting or removing workers from hazardous atmospheres. 

The Standards Completion Program 

In 1974, NIOSH and OSHA jointly initiated the development of occupational health standards 

consistent with Section 6(b) of the Occupational Safety and Health Act of 1970 for substances 

with then-existing OSHA permissible exposure limits (PELs). This joint effort was called the 

Standards Completion Program (SCP) and involved the cooperative efforts of personnel from 

various divisions within NIOSH and OSHA, and several contractors. The SCP developed 387 

substance-specific draft standards with supporting documentation that contained technical 

information and recommendations needed for the promulgation of new occupational health 

regulations. Although new standards were not promulgated at that time, these data became the 

original basis for the NIOSH/OSHA Occupational Health Guidelines for Chemical Hazards 

[NIOSH/OSHA 1981]. 

As part of the respirator selection process for each draft technical standard, an IDLH value was 

determined. The definition for an IDLH value that was derived during the SCP was based on 

the definition stipulated in 30 CFR 11.3(t). The purpose for establishing this IDLH value was to 

determine a concentration from which a worker could escape without injury or without 

irreversible health effects in the event of respiratory protection equipment failure (e.g., 

contaminant breakthrough in a cartridge respirator or stoppage of air flow in a supplied-air 

respirator) and a concentration above which only "highly reliable" respirators would be 

required. In determining IDLH values, the ability of a worker to escape without loss of life or 

irreversible health effects was considered along with severe eye or respiratory irritation and 

other deleterious effects (e.g., disorientation or incoordination) that could prevent escape. 

Although in most cases, egress from a particular worksite could occur in much less than 30 

minutes, as a safety margin, IDLH values were based on the effects that might occur as a 

consequence of a 30-minute exposure. However, the 30-minute period was NOT meant to 

imply that workers should stay in the work environment any longer than necessary following 

the failure of respiratory protection equipment; in fact, EVERY EFFORT SHOULD BE 

MADE TO EXIT IMMEDIATELY!

IDLH values were determined for each substance during the SCP on a case-by-case basis, 

taking into account the toxicity data available at the time. Whenever possible, IDLH values 

were determined using health effects data from studies of humans exposed for short durations. 

However, in most instances, a lack of human data necessitated the use of animal toxicity data. 

When inhalation studies of animals exposed for short durations (i.e., 0.5 to 4 hours) were the 

only health effects data available, IDLH values were based on the lowest exposure causing 

death or irreversible health effects in any species. When lethal dose (LD) data from animals 

were used, IDLH values were estimated on the basis of an equivalent exposure to a 70-kg 

worker breathing 10 cubic meters of air. 

Since chronic exposure data may have little relevance to acute effects, these types of data were 

used in determining IDLH values only when no acute toxicity data were available and only in 

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conjunction with competent scientific judgment. In a number of instances when no relevant 

human or animal toxicity data were available, IDLH values were based on analogies with other 

substances with similar toxic effects.

Discussion of the Original IDLH Values 

The basis for each of the 387 IDLH values determined during the SCP were reviewed and 

paraphrased from the individual draft technical standards for this publication. Also included is 

a complete listing of references cited in the SCP; in many cases where only secondary 

references were cited, the original sources have also been added. Whenever available, the 

references (secondary and primary) were obtained to verify the information cited in the SCP. 

However, a few of the original references, such as personal communications and foreign 

reports, could not be located.

Although 387 substances were originally included in the SCP, IDLH values were not 

specifically determined for all of them. The published data at that time for 40 of these 

substances (e.g., DDT and triphenyl phosphate) showed no evidence that an acute exposure to 

high concentrations would impede escape or cause any irreversible health effects following a 

30-minute exposure and the designation "NO EVIDENCE" was used in the listing of IDLHs. 

For all of these substances, respirators were selected on the basis of assigned protection 

factors. For some (e.g., copper fume and tetryl), an assigned protection factor of 2,000 times 

the PEL was arbitrarily used to determine the concentration above which only the "most 

protective" respirators were permitted. However, for most particulate substances for which 

evidence for establishing an IDLH value did not exist (e.g., ferbam and oil mist), the use of an 

assigned protection factor of 2,000 would have resulted in the assignment of respirators at 

concentrations that were not likely to be encountered in the occupational environment. In 

addition, exposure concentrations greater than 500 times the PEL for many airborne 

particulates could result in exposures that would hamper vision. Therefore, it was decided as 

part of the SCP (and during the review and revision of the IDLH values) that for such 

particulate substances, only the "most protective" respirators would be permitted for use in 

concentrations exceeding 500 times the PEL. 

IDLH values could not be determined during the SCP for 22 substances (e.g., bromoform and 

calcium oxide) because of a lack of relevant toxicity data and therefore the designation 

"UNKNOWN" was used in the IDLH value listing. For most of these substances, the 

concentrations above which only the "most protective" respirators were allowed were based 

arbitrarily on assigned protection factors that ranged from 10 to 2,000 times the PEL, 

depending on the substance. There were also 10 substances (e.g., n-pentane and ethyl ether) 

for which it was determined only that the IDLH values were in excess of the lower explosive 

limits (LELs). Therefore, the LEL was selected as the IDLH value with the designation "LEL" 

added in the IDLH listing. For these substances, only the "most protective" respirators were 

permitted above the LEL in the SCP draft technical standards. 

For 14 substances (e.g., beryllium and endrin), the IDLH values determined during the SCP 

were greater than the concentrations permitted based on assigned respiratory protection 

factors. In most instances the IDLHs for these substances were set at concentrations 2,000 

times the PEL.

Current NIOSH Use of IDLH Values

The current NIOSH definition for an IDLH condition, as given in the NIOSH Respirator 

Selection Logic, is one that poses a threat of exposure to airborne contaminants when that 

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exposure is likely to cause death or immediate or delayed permanent adverse health effects or 

prevent escape from such an environment [NIOSH 2004]. The purpose of establishing an 

IDLH value is (1) to ensure that the worker can escape from a given contaminated environment 

in the event of failure of the respiratory protection equipment and (2) is considered a 

maximum level above which only a highly reliable breathing apparatus providing maximum 

worker protection is permitted [NIOSH 2004]. In establishing the IDLH value, the following 

conditions must be assured:

A. The ability to escape without loss of life or immediate or delayed irreversible health effects. 

(Thirty minutes is considered the maximum time for escape so as to provide some margin of 

safety in calculating an IDLH value.)

B. The prevention of severe eye or respiratory irritation or other reactions that would hinder 

escape.

The NIOSH respirator decision logic uses an IDLH value as one of several respirator selection 

criteria. Under the NIOSH respirator decision logic, "highly reliable" respirators (i.e., the most 

protective respirators) would be selected for emergency situations, fire fighting, exposure to 

carcinogens, entry into oxygen-deficient atmospheres, entry into atmospheres that contain a 

substance at a concentration greater than 2,000 times the NIOSH REL or OSHA PEL, and for 

entry into immediately dangerous to life or health conditions. These "highly reliable" 

respirators include either a self-contained breathing apparatus (SCBA) that has a full facepiece 

and is operated in a pressure-demand or other positive-pressure mode, or a supplied-air 

respirator that has a full facepiece and is operated in a pressure-demand or other positivepressure mode in combination with an auxiliary SCBA operated in a pressure-demand or other 

positive-pressure mode. 

When the IDLH values were developed in the mid-1970's, only limited toxicological data were 

available for many of the substances. In 1993, NIOSH requested information on the uses of 

IDLH values in the workplace and on the scientific adequacy of the criteria and procedures 

originally used for establishing them [Federal Register, Volume 58, Number 229, p. 63379, 

Wednesday, December 1, 1993]. The information received in response to the Federal Register 

announcement was evaluated and used to establish future actions concerning IDLH values. 

This document includes IDLH values for 85 substances (e.g., benzene and methylene chloride) 

determined by NIOSH to meet the OSHA definition of "potential occupational carcinogen" as 

given in 29 CFR 1990.103. For all of these substances, except ethylene oxide and crystalline 

silica, NIOSH recommends that the "most protective" respirators be worn by workers exposed 

at concentrations above the NIOSH REL, or at any detectable concentration when there is no 

REL. For ethylene oxide and crystalline silica, NIOSH recommends that the "most protective" 

respirators be worn in concentrations exceeding 5 ppm and 25 mg/m3, respectively [NIOSH 

1989, 2005].

Revised Criteria for Determining IDLH Values 

The criteria utilized to determine the adequacy of existing IDLH values were a combination of 

those used during the SCP and a newer methodology developed by NIOSH. These criteria form 

a tiered approach with acute human toxicity data being used preferentially, followed next by 

acute animal inhalation toxicity data, and then finally by acute animal oral toxicity data to 

determine an updated IDLH value. When relevant acute toxicity data were insufficient or 

unavailable, then the use of chronic toxicity data or an analogy to a chemical with similar toxic 

effects was considered. In order to facilitate the revision process, secondary toxicological data 

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were primarily used. Once a preliminary IDLH value was developed, it was compared to the 

existing IDLH value and to several other factors (e.g., existing short-term exposure guidelines 

and lower explosive limits). 

The following "hierarchy" was followed to develop a "preliminary" value for the revised IDLH 

value: 

A.Human acute toxicity data were used if sufficient to determine a concentration that for up to 

30 minutes does not cause death, serious or irreversible health effects, or does not impair or 

impede the ability to escape.

B.Animal acute lethal concentration (LC) data were considered next. The only animal lethal 

concentration data used involved mammals; the vast majority of the data was from studies of 

rats, mice, guinea pigs, and hamsters. It was decided to generally use the lowest reliable LC 

data, with LC50 data preferred. If acute LC data determined during a 30-minute period were 

not available, then the data, based on a study by ten Berge et al. [1986], were "adjusted" to an 

equivalent 30-minute value using the following relationship:

Adjusted LC50 (30 minutes) = LC50(t) * (t/0.5)** (1/n) 

where: LC50(t) = LC50 determined over t hours

n = constant*

*Note: ten Berge et al. [1986] determined the relationship shown above based on experimental 

data. The constant "n" was determined by ten Berge et al. to be less than 3.0 for 18 of the 20 

substances studied. Although the individual "n" values determined by ten Berge et al. [1986] 

were utilized when applicable during the review and revision of the original IDLHs, as a 

conservative estimate, an "n" = 3.0 was assumed when "adjusting" the LC data to 30 minutes 

for all other substances.

This equation with an "n" = 3.0 results in the following correction factors:

t(hours) correction factor

O.5 1.0

1 1.25

2 1.6

3 1.8

4 2.0

5 2.15

6 2.3

7 2.4

8 2.5

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The LC values (after "adjusting" if necessary to 30 minutes) were divided by a safety factor of 

10 to determine a "preliminary" IDLH for comparison purposes.

C.Animal lethal dose (LD) data were considered next. As was the case with the lethal 

concentration data, the only animal lethal dose data used involved mammals; the vast majority 

of the data were from studies of rats, mice, guinea pigs, and hamsters. It was decided to 

generally use the lowest LD data with oral LD50 data preferred. The LD data was used to 

determine the equivalent total dose to a 70-kg worker and, as was done during the SCP, the air 

concentration containing this dose was determined by dividing by 10 cubic meters. [Note: A 

worker breathing at a rate of 50 liters per minute for 30 minutes would inhale 1.5 cubic meters 

of air.] A "preliminary" IDLH for comparison purposes was determined by dividing these air 

concentrations by a safety factor of 10. D. Chronic toxicity data were considered if no relevant 

acute toxicity data existed. However, the fact that chronic exposures may have limited 

relevance to acute effects was taken into consideration.

E. When relevant toxicity data applying specifically to the chemicals in question were lacking, 

and if it was determined to be justified, then analogies to substances with similar acute toxic 

effects were considered. F. All "preliminary" IDLHs derived during this update were checked 

against the following factors prior to establishing the final "revised" IDLH: 

1. Lower explosive limit (LEL): It was decided to restrict the "routine" entry into a possible 

explosive atmosphere to concentrations no greater than 10% of the LEL. [Note: SCPderived IDLHs were set at 100% of the LELs if there were no known serious health 

hazards below these values. However, OSHA considers concentrations in excess of 10% of 

the LEL to be a hazardous atmosphere in confined spaces [29 CFR 1910.146(b)].]

2. RD50 data: An RD50 is defined as the 10-minute exposure concentration producing a 

50% respiratory rate decrease in mice or rats and can be used to estimate severe 

respiratory irritation. Prolonged exposure to an RD50 concentration has been shown to 

produce respiratory tract lesions consistent with irritation [Alarie 1981; Buckley et al. 

1984].

3. Other short-term exposure guidelines such as the American Industrial Hygiene 

Association's emergency response planning guidelines (ERPGs) and the National 

Research Council's emergency exposure guidance levels (EEGLs) and short-term public 

emergency guidance levels (SPEGLs), and occupational exposure standards or 

recommendations such as OSHA PELs, NIOSH RELs, or the American Conference of 

Governmental Industrial Hygienists (ACGIH) TLVs.

4. Based on the NIOSH respirator decision logic, the revised IDLH values could not be 

greater than 2,000 times the NIOSH REL (or OSHA PEL). 

5. The revised IDLH values would not be greater than the original IDLH values derived 

during the SCP.

Anyone who is aware of additional published data that may affect the IDLH values determined 

for particular substances is encouraged to make this information available to NIOSH. All data 

will be reviewed and consideration will be made regarding subsequent revision of the IDLH 

values.

References

Alarie Y [1981]. Dose-response analysis in animal studies: prediction of human responses. 

Environ Health Persp 42:9-13. 

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Centers for Disease Control and Prevention 1600 Clifton Rd. Atlanta, GA 

30333, USA

800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO

Buckley LA, Jiang XZ, James RA, Morgan KT, Barrow CS [1984]. Respiratory tract lesions 

induced by sensory irritants at the RD50 concentration. Toxicol Appl Pharacol 74(3):417-429. 

NIOSH/OSHA [1981]. Occupational health guidelines for chemical hazards. Cincinnati, OH: 

U.S. Department of Health and Human Services, Public Health Service, Centers for Disease 

Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 

No. 81-123 (NTIS Publication No. PB-83-154609). 

NIOSH [1989]. Current Intelligence Bulletin 52. Ethylene oxide sterilizers in health care 

facilities. Engineering controls and work practices. Cincinnati, OH: U.S. Department of Health 

and Human Services, Public Health Service, Centers for Disease Control, National Institute for 

Occupational Safety and Health, DHHS (NIOSH) Publication No. 89-115 (NTIS Publication 

No. PB-90-142571). 

NIOSH [2004]. NIOSH respirator selection logic. Cincinnati, OH: U.S. Department of Health 

and Human Services, Public Health Service, Centers for Disease Control, National Institute for 

Occupational Safety and Health, DHHS (NIOSH). Publication No. 2005-100.

NIOSH [2005]. NIOSH Pocket Guide to Chemical Hazards. Cincinnati, OH: U.S. Department 

of Health and Human Services, Public Health Service, Centers for Disease Control, National 

Institute for Occupational Safety and Health, DHHS (NIOSH). Publication No. 2005-149.

ten Berge WF, Zwart A, Appleman LM [1986]. Concentration-time mortality response 

relationship of irritant and systematically acting vapours and gases. J Haz Mat 13:301-309. 

Yant WP [1944]. Protecting workers against temporary and emergency exposures. In: 

Protecting plant manpower through the control of air contaminants. Special Bulletin No. 14. 

Washington, DC: U.S. Department of Labor, Division of Labor Standards. 

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May 1994

Documentation for Immediately Dangerous To Life or Health

Concentrations (IDLHs)

Chemical Listing and Documentation of Revised IDLH

Values (as of 3/1/95)

Substance Original IDLH

Value

Revised IDLH

Value

Acetaldehyde (75070.html) 10,000 ppm 2,000 ppm

Acetic acid (64197.html) 1,000 ppm 50 ppm

Acetic anhydride (108247.html) 1,000 ppm 200 ppm

Acetone (67641.html) 20,000 ppm 2,500 ppm [LEL]

Acetonitrile (75058.html) 4,000 ppm 500 ppm

Acetylene tetrabromide (79276.html) 10 ppm 8 ppm

Acrolein (107028.html) 5 ppm 2 ppm

Acrylamide (79061.html) Unknown 60 mg/m

Acrylonitrile (107131.html) 500 ppm 85 ppm

Aldrin (309002.html) 100 mg/m 25 mg/m

Allyl alcohol(107186.html) 150 ppm 20 ppm

Allyl chloride (107051.html) 300 ppm 250 ppm

Allyl glycidyl ether (106923.html) 270 ppm 50 ppm

2 Aminopyridine (504290.html) 5 ppm 5 ppm [Unch]

Ammonia (7664417.html) 500 ppm 300 ppm

Ammonium sulfamate (7773060.html) 5,000 mg/m 1,500 mg/m

n-Amyl acetate (628637.html) 4,000 ppm 1,000 ppm

sec-Amyl acetate (626380.html) 9,000 ppm 1,000 ppm

3

3 3

3 3
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Aniline (62533.html) 100 ppm 100 ppm [Unch]

o-Anisidine (90040.html) 50 mg/m 50 mg/m [Unch]

p-Anisidine (104949.html) 50 mg/m 50 mg/m [Unch]

Antimony compounds (as Sb)(7440360.html) 80 mg Sb/m 50 mg Sb/m

ANTU (86884.html) 100 mg/m 100 mg/m

[Unch]

Arsenic (inorganic compounds, as As) (7440382.html) 100 mg As/m 5 mg As/m

Arsine (7784421.html) 6 ppm 3 ppm

Azinphosmethyl(86500.html) 20 mg/m 10 mg/m

Barium (soluble compounds, as Ba) (7440393.html) 1,100 mg Ba/m 50 mg Ba/m

Benzene (71432.html) 3,000 ppm 500 ppm

Benzoyl peroxide (94360.html) 7,000 mg/m 1,500 mg/m

Benzyl chloride (100447.html) 10 ppm 10 ppm [Unch]

Beryllium compounds (as Be)(7440417.html) 10 mg Be/m 4 mg Be/m

Boron oxide (1303862.html) N.E. 2,000 mg/m

Boron trifluoride (7637072.html) 100 ppm 25 ppm

Bromine (7726956.html) 10 ppm 3 ppm

Bromoform (75252.html) Unknown 850 ppm

1,3-Butadiene (106990.html) 20,000 ppm

[LEL]

2,000 ppm [LEL]

2-Butanone (78933.html) 3,000 ppm 3,000 ppm

[Unch]

2-Butoxyethanol(111762.html) 700 ppm 700 ppm [Unch]

n-Butyl acetate (123864.html) 10,000 ppm 1,700 ppm [LEL]

sec-Butyl acetate (105464.html) 10,000 ppm 1,700 ppm [LEL]

tert-Butyl acetate (540885.html) 10,000 ppm 1,500 ppm [LEL]

n-Butyl alcohol(71363.html) 8,000 ppm 1,400 ppm [LEL]

sec-Butyl alcohol(78922.html) 10,000 ppm 2,000 ppm

tert-Butyl alcohol(75650.html) 8,000 ppm 1,600 ppm

n-Butylamine (109739.html) 2,000 ppm 300 ppm

tert-Butyl chromate (1189851.html) 30 mg/m (as

CrO3)

15 mg Cr(VI)/m

3 3

3 3

3 3

3 3

3 3

3 3

3 3

3 3

3 3

3

3 3
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CrO3)

n-Butyl glycidyl ether (2426086.html) 3,500 ppm 250 ppm

n-Butyl mercaptan (109795.html) 2,500 ppm 500 ppm

p-tert-Butyltoluene (98511.html) 1,000 ppm 100 ppm

Cadmium dust (as Cd) (7440439.html) 50 mg Cd/m 9 mg Cd/m

Cadmium fume (as Cd) (7440439.html) 9 mg Cd/m 9 mg Cd/m [Unc

h]

Calcium arsenate (as As) (7778441.html) 100 mg As/m 5 mg As/m

Calcium oxide (1305788.html) Unknown 25 mg/m

Camphor (synthetic) (76222.html) 200 mg/m 200 mg/m

[Unch]

Carbaryl(63252.html) 600 mg/m 100 mg/m

Carbon black (1333864.html) N.E. 1,750 mg/m

Carbon dioxide (124389.html) 50,000 ppm 40,000 ppm

Carbon disulfide (75150.html) 500 ppm 500 ppm [Unch]

Carbon monoxide (630080.html) 1,500 ppm 1,200 ppm

Carbon tetrachloride (56235.html) 300 ppm 200 ppm

Chlordane (57749.html) 500 mg/m 100 mg/m

Chlorinated camphene (8001352.html) 200 mg/m 200 mg/m

[Unch]

Chlorinated diphenyl oxide (31242930.html) Unknown 5 mg/m

Chlorine (7782505.html) 30 ppm 10 ppm

Chlorine dioxide (10049044.html) 10 ppm 5 ppm

Chlorine trifluoride (7790912.html) 20 ppm 20 ppm [Unch]

Chloroacetaldehyde (107200.html) 100 ppm 45 ppm

alpha-Chloroacetophenone (532274.html) 100 mg/m 15 mg/m

Chlorobenzene (108907.html) 2,400 ppm 1,000 ppm

o-Chlorobenzylidene malononitrile (2698411.html) 2 mg/m 2 mg/m [Unch]

Chlorobromomethane (74975.html) 5,000 ppm 2,000 ppm

Chlorodiphenyl (42% chlorine)(53469219.html) 10 mg/m 5 mg/m

Chlorodiphenyl (54% chlorine)(53469219.html) 5 mg/m 5 mg/m [Unch]

Chloroform (67663.html) 1,000 ppm 500 ppm

3 3

3 3

3 3

3

3 3

3 3

3

3 3

3 3

3

3 3

3 3

3 3

3 3
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1-Chloro-1-nitropropane (600259.html) 2,000 ppm 100 ppm

Chloropicrin (76062.html) 4 ppm 2 ppm

beta-Chloroprene (126998.html) 400 ppm 300 ppm

Chromic acid and chromates (1333820.html) 30 mg/m (as

CrO3)

15 mg Cr(VI)/m

Chromium (II) compounds [as Cr(II)](Cr2M3.html) N.E. 250 mg

Cr(II)/m

Chromium (III) compounds [as Cr(III)] (Cr3M3.html) N.E. 25 mg Cr(III)/m

Chromium metal (as Cr) (7440473.html) N.E. 250 mg Cr/m

Coal tar pitch volatiles (65996932.html) 700 mg/m 80 mg/m

Cobalt metal, dust and fume (as Co)(7440484.html) 20 mg Co/m 20 mg Co/m

[Unch]

Copper (dusts and mists, as Cu)(7440508.html) N.E. 100 mg Cu/m

Copper fume (as Cu) (1317380.html) N.E. 100 mg Cu/m

Cotton dust (raw)(cotdust.html) N.E. 100 mg/m

Crag (r) herbicide (136787.html) 5,000 mg/m 500 mg/m

Cresol (o, m, p isomers) (cresol.html) 250 ppm 250 ppm [Unch]

Crotonaldehyde (123739.html) 400 ppm 50 ppm

Cumene (98828.html) 8,000 ppm 900 ppm [LEL]

Cyanides (as CN)(cyanides.html) 50 mg/m (as

CN)

25 mg/m (as

CN)

Cyclohexane (110827.html) 10,000 ppm 1,300 ppm [LEL]

Cyclohexanol(108930.html) 3,500 ppm 400 ppm

Cyclohexanone (108941.html) 5,000 ppm 700 ppm

Cyclohexene (110838.html) 10,000 ppm 2,000 ppm

Cyclopentadiene (542927.html) 2,000 ppm 750 ppm

2,4-D(94757.html) 500 mg/m 100 mg/m

DDT (50293.html) N.E. 500 mg/m

Decaborane (17702419.html) 100 mg/m 15 mg/m

Demeton (8065483.html) 20 mg/m 10 mg/m

Diacetone alcohol(123422.html) 2,100 ppm 1,800 ppm [LEL]

3 3

3

3

3

3 3

3 3

3

3

3

3 3

3 3

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3

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Diazomethane (334883.html) 2 ppm 2 ppm [Unch]

Diborane (19287457.html) 40 ppm 15 ppm

Dibutyl phosphate (107664.html) 125 ppm 30 ppm

Dibutyl phthalate (84742.html) 9,300 mg/m 4,000 mg/m

o-Dichlorobenzene (95501.html) 1,000 ppm 200 ppm

p-Dichlorobenzene (106467.html) 1,000 ppm 150 ppm

Dichlorodifluoromethane (75718.html) 50,000 ppm 15,000 ppm

1,3-Dichloro 5,5-dimethylhydantoin (118525.html) Unknown 5 mg/m

1,1-Dichloroethane (75343.html) 4,000 ppm 3,000 ppm

1,2-Dichloroethylene (540590.html) 4,000 ppm 1,000 ppm

Dichloroethyl ether (111444.html) 250 ppm 100 ppm

Dichloromonofluoromethane (75434.html) 50,000 ppm 5,000 ppm

1,1-Dichloro 1-nitroethane (594729.html) 150 ppm 25 ppm

Dichlorotetrafluoroethane (76142.html) 50,000 ppm 15,000 ppm

Dichlorvos (62737.html) 200 mg/m 100 mg/m

Dieldrin (60571.html) 450 mg/m 50 mg/m

Diethylamine (109897.html) 2,000 ppm 200 ppm

2-Diethylaminoethanol(100378.html) 500 ppm 100 ppm

Difluorodibromomethane (75616.html) 2,500 ppm 2,000 ppm

Diglycidyl ether (2238075.html) 25 ppm 10 ppm

Diisobutyl ketone (108838.html) 2,000 ppm 500 ppm

Diisopropylamine (108189.html) 1,000 ppm 200 ppm

Dimethyl acetamide (127195.html) 400 ppm 300 ppm

Dimethylamine (124403.html) 2,000 ppm 500 ppm

N,N-Dimethylaniline (121697.html) 100 ppm 100 ppm [Unch]

Dimethyl 1,2-dibromo 2,2-dichlorethyl phosphate

(300765.html)

1,800 mg/m 200 mg/m

Dimethylformamide (68122.html) 3,500 ppm 500 ppm

1,1-Dimethylhydrazine (57147.html) 50 ppm 15 ppm

Dimethylphthalate (131113.html) 9,300 mg/m 2,000 mg/m

Dimethyl sulfate (77781.html) 10 ppm 7 ppm

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Dinitrobenzene (o, m, p isomers)(528290.html) 200 mg/m 50 mg/m

Dinitroocresol(534521.html) 5 mg/m 5 mg/m [Unch]

Dinitrotoluene (25321146.html) 200 mg/m 50 mg/m

Di sec-octyl phthalate (117817.html) Unknown 5,000 mg/m

Dioxane (123911.html) 2,000 ppm 500 ppm

Diphenyl(92524.html) 300 mg/m 100 mg/m

Dipropylene glycol methyl ether (34590948.html) Unknown 600 ppm

Endrin (72208.html) 2,000 mg/m 2 mg/m

Epichlorohydrin (106898.html) 250 ppm 75 ppm

EPN (2104645.html) 50 mg/m 5 mg/m

Ethanolamine (141435.html) 1,000 ppm 30 ppm

2-Ethoxyethanol(110805.html) 6,000 ppm 500 ppm

2-Ethoxyethyl acetate (111159.html) 2,500 ppm 500 ppm

Ethyl acetate (141786.html) 10,000 ppm 2,000 ppm [LEL]

Ethyl acrylate (140885.html) 2,000 ppm 300 ppm

Ethyl alcohol(64175.html) 15,000 ppm 3,300 ppm [LEL]

Ethylamine (75047.html) 4,000 ppm 600 ppm

Ethyl benzene (100414.html) 2,000 ppm 800 ppm [LEL]

Ethyl bromide (74964.html) 3,500 ppm 2,000 ppm

Ethyl butyl ketone (106354.html) 3,000 ppm 1,000 ppm

Ethyl chloride (75003.html) 20,000 ppm 3,800 ppm [LEL]

Ethylene chlorohydrin (107073.html) 10 ppm 7 ppm

Ethylenediamine (107153.html) 2,000 ppm 1,000 ppm

Ethylene dibromide (106934.html) 400 ppm 100 ppm

Ethylene dichloride (107062.html) 1,000 ppm 50 ppm

Ethylene glycol dinitrate (628966.html) 500 mg/m 75 mg/m

Ethyleneimine (151564.html) 100 ppm 100 ppm [Unch]

Ethylene oxide (75218.html) 800 ppm 800 ppm [Unch]

Ethyl ether (60297.html) 19,000 ppm

[LEL]

1,900 ppm [LEL]

Ethyl formate (109944.html) 8,000 ppm 1,500 ppm

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Ethyl mercaptan (75081.html) 2,500 ppm 500 ppm

N-Ethylmorpholine (100743.html) 2,000 ppm 100 ppm

Ethyl silicate (78104.html) 1,000 ppm 700 ppm

Ferbam (14484641.html) N.E. 800 mg/m

Ferrovanadium dust (12604589.html) N.E. 500 mg/m

Fluorides (as F)(fluoride.html) 500 mg F/m 250 mg F/m

Fluorine (7782414.html) 25 ppm 25 ppm [Unch]

Fluorotrichloromethane (75694.html) 10,000 ppm 2,000 ppm

Formaldehyde (50000.html) 30 ppm 20 ppm

Formic acid (64186.html) 30 ppm 30 ppm [Unch]

Furfural(98011.html) 250 ppm 100 ppm

Furfuryl alcohol(98000.html) 250 ppm 75 ppm

Glycidol(556525.html) 500 ppm 150 ppm

Graphite (natural) (7782425.html) N.E. 1,250 mg/m

Hafnium compounds (as Hf) (7440586.html) Unknown 50 mg Hf/m

Heptachlor (76448.html) 700 mg/m 35 mg/m

n-Heptane (142825.html) 5,000 ppm 750 ppm

Hexachloroethane (67721.html) 300 ppm 300 ppm [Unch]

Hexachloronaphthalene (1335871.html) 2 mg/m 2 mg/m [Unch]

n-Hexane (110543.html) 5,000 ppm 1,100 ppm [LEL]

2-Hexanone (591786.html) 5,000 ppm 1,600 ppm

Hexone (108101.html) 3,000 ppm 500 ppm

sec Hexyl acetate (108849.html) 4,000 ppm 500 ppm

Hydrazine (302012.html) 80 ppm 50 ppm

Hydrogen bromide (10035106.html) 50 ppm 30 ppm

Hydrogen chloride (7647010.html) 100 ppm 50 ppm

Hydrogen cyanide (74908.html) 50 ppm 50 ppm [Unch]

Hydrogen fluoride (as F)(7664393.html) 30 ppm 30 ppm [Unch]

Hydrogen peroxide (772841.html) 75 ppm 75 ppm [Unch]

Hydrogen selenide (as Se) (7783075.html) 2 ppm 1 ppm

3

3

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3

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Hydrogen sulfide (7783064.html) 300 ppm 100 ppm

Hydroquinone (123319.html) Unknown 50 mg/m

Iodine (7553562.html) 10 ppm 2 ppm

Iron oxide dust and fume (as Fe) (1309371.html) N.E. 2,500 mg Fe/m

Isoamyl acetate (123922.html) 3,000 ppm 1,000 ppm

Isoamyl alcohol (primary and secondary)(123513.html) 10,000 ppm 500 ppm

Isobutyl acetate (110190.html) 7,500 ppm 1,300 ppm [LEL]

Isobutyl alcohol(78831.html) 8,000 ppm 1,600 ppm

Isophorone (78591.html) 800 ppm 200 ppm

Isopropyl acetate (108214.html) 16,000 ppm 1,800 ppm

Isopropyl alcohol(67630.html) 12,000 ppm 2,000 ppm [LEL]

Isopropylamine (75310.html) 4,000 ppm 750 ppm

Isopropyl ether (108203.html) 10,000 ppm 1,400 ppm [LEL]

Isopropyl glycidyl ether (4016142.html) 1,000 ppm 400 ppm

Ketene (463514.html) Unknown 5 ppm

Lead compounds (as Pb)(7439921.html) 700 mg Pb/m 100 mg Pb/m

Lindane (58899.html) 1,000 mg/m 50 mg/m

Lithium hydride (7580678.html) 55 mg/m 0.5 mg/m

L.P.G. (68476857.html) 19,000 ppm

[LEL]

2,000 ppm [LEL]

Magnesium oxide fume (1309484.html) N.E. 750 mg/m

Malathion (121755.html) 5,000 mg/m 250 mg/m

Maleic anhydride (108316.html) Unknown 10 mg/m

Manganese compounds (as Mn)(7439965.html) N.E. 500 mg Mn/m

Mercury compounds [except (organo) alkyls, as Hg]

(7439976.html)

28 mg Hg/m 10 mg Hg/m

Mercury (organo) alkyl compounds(as Hg) (merchg.html)10 mg Hg/m 2 mg Hg/m

Mesityl oxide (141797.html) 5,000 ppm 1,400 ppm [LEL]

Methoxychlor (72435.html) N.E. 5,000 mg/m

Methyl acetate (79209.html) 10,000 ppm 3,100 ppm [LEL]

Methyl acetylene (74997.html) 15,000 ppm 1,700 ppm [LEL]

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3

3 3

3 3

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3

3 3

3

3

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Methyl acetylene (74997.html) 15,000 ppm

[LEL]

1,700 ppm [LEL]

Methyl acetylenepropadiene mixture (59355758.html) 15,000 ppm 3,400 ppm [LEL]

Methyl acrylate (96333.html) 1,000 ppm 250 ppm

Methylal(109875.html) 15,000 ppm

[LEL]

2,200 ppm [LEL]

Methyl alcohol(67561.html) 25,000 ppm 6,000 ppm

Methylamine (74895.html) 100 ppm 100 ppm [Unch]

Methyl (namyl) ketone (110430.html) 4,000 ppm 800 ppm

Methyl bromide (74839.html) 2,000 ppm 250 ppm

Methyl Cellosolve (r)(109864.html) 2,000 ppm 200 ppm

Methyl Cellosolve (r) acetate (110496.html) 4,000 ppm 200 ppm

Methyl chloride (74873.html) 10,000 ppm 2,000 ppm

Methyl chloroform (71556.html) 1,000 ppm 700 ppm

Methylcyclohexane (108872.html) 10,000 ppm 1,200 ppm [LEL]

Methylcyclohexanol(25639423.html) 10,000 ppm 500 ppm

o-Methylcyclohexanone (583608.html) 2,500 ppm 600 ppm

Methylene bisphenyl isocyanate (101688.html) 100 mg/m 75 mg/m

Methylene chloride (75092.html) 5,000 ppm 2,300 ppm

Methyl formate (107313.html) 5,000 ppm 4,500 ppm

5-Methyl 3-heptanone (541855.html) 3,000 ppm 100 ppm

Methyl hydrazine (60344.html) 50 ppm 20 ppm

Methyl iodide (74884.html) 800 ppm 100 ppm

Methyl isobutyl carbinol(108112.html) 2,000 ppm 400 ppm

Methyl isocyanate (624839.html) 20 ppm 3 ppm

Methyl mercaptan (74931.html) 400 ppm 150 ppm

Methyl methacrylate (80626.html) 4,000 ppm 1,000 ppm

Methyl styrene (98839.html) 5,000 ppm 700 ppm

Mica (12001262.html) N.E. 1,500 mg/m

Molybdenum (insoluble compounds, as Mo)

(7439987.html)

N.E. 5,000 mg Mo/m

Molybdenum (soluble compounds, as Mo) (molymo.html)N.E. 1,000 mg Mo/m

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3

3

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mo.html)

Monomethyl aniline (100618.html) 100 ppm 100 ppm [Unch]

Morpholine (110918.html) 8,000 ppm 1,400 ppm [LEL]

Naphtha (coal tar) (8030306.html) 10,000 ppm

[LEL]

1,000 ppm [LEL]

Naphthalene (91203.html) 500 ppm 250 ppm

Nickel carbonyl (as Ni) (13463393.html) 7 ppm 2 ppm

Nickel metal and other compounds (as Ni)

(7440020.html)

N.E. 10 mg Ni/m

Nicotine (54115.html) 35 mg/m 5 mg/m

Nitric acid (7697372.html) 100 ppm 25 ppm

Nitric oxide (10102439.html) 100 ppm 100 ppm [Unch]

p-Nitroaniline (100016.html) 300 mg/m 300 mg/m

[Unch]

Nitrobenzene (98953.html) 200 ppm 200 ppm [Unch]

p-Nitrochlorobenzene (100005.html) 1,000 mg/m 100 mg/m

Nitroethane (79243.html) 1,000 ppm 1,000 ppm

[Unch]

Nitrogen dioxide (10102440.html) 50 ppm 20 ppm

Nitrogen trifluoride (7783542.html) 2,000 ppm 1,000 ppm

Nitroglycerine (55630.html) 500 mg/m 75 mg/m

Nitromethane (75525.html) 1,000 ppm 750 ppm

1-Nitropropane (108032.html) 2,300 ppm 1,000 ppm

2-Nitropropane (79469.html) 2,300 ppm 100 ppm

Nitrotoluene (o, m, p isomers) (88722.html) 200 ppm 200 ppm [Unch]

Octachloronaphthalene (2234131.html) Unknown Unknown [Unch]

Octane (111659.html) 5,000 ppm 1,000 ppm [LEL]

Oil mist (mineral)(8012951.html) N.E. 2,500 mg/m

Osmium tetroxide (as Os) (20816120.html) 1 mg Os/m 1 mg Os/m

[Unch]

Oxalic acid (144627.html) 500 mg/m 500 mg/m

[Unch]

Oxygen difluoride (7783417.html) 0.5 ppm 0.5 ppm [Unch]

Ozone (10028156.html) 10 ppm 5 ppm

3

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Ozone (10028156.html) 10 ppm 5 ppm

Paraquat (1910425.html) 1.5 mg/m 1 mg/m

Parathion (56382.html) 20 mg/m 10 mg/m

Pentaborane (19624227.html) 3 ppm 1 ppm

Pentachloronaphthalene (1321648.html) Unknown Unknown [Unch]

Pentachlorophenol(87865.html) 150 mg/m 2.5 mg/m

n-Pentane (109660.html) 15,000 ppm

[LEL]

1,500 ppm [LEL]

2-Pentanone (107879.html) 5,000 ppm 1,500 ppm

Perchloromethyl mercaptan (594423.html) 10 ppm 10 ppm [Unch]

Perchloryl fluoride (7616946.html) 385 ppm 100 ppm

Petroleum distillates (naphtha)(8002059.html) 10,000 ppm 1,100 ppm [LEL]

Phenol(108952.html) 250 ppm 250 ppm [Unch]

p-Phenylene diamine (106503.html) Unknown 25 mg/m

Phenyl ether (vapor)(101848.html) N.E. 100 ppm

Phenyl etherbiphenyl mixture (vapor)(8004135.html) N.E. 10 ppm

Phenyl glycidyl ether (122601.html) Unknown 100 ppm

Phenylhydrazine (100630.html) 295 ppm 15 ppm

Phosdrin (7786347.html) 4 ppm 4 ppm [Unch]

Phosgene (75445.html) 2 ppm 2 ppm [Unch]

Phosphine (7803512.html) 200 ppm 50 ppm

Phosphoric acid (7664382.html) 10,000 mg/m 1,000 mg/m

Phosphorus (yellow)(7723140.html) N.E. 5 mg/m

Phosphorus pentachloride (10026138.html) 200 mg/m 70 mg/m

Phosphorus pentasulfide (1314803.html) 750 mg/m 250 mg/m

Phosphorus trichloride (7719122.html) 50 ppm 25 ppm

Phthalic anhydride (85449.html) 10,000 mg/m 60 mg/m

Picric acid (88891.html) 100 mg/m 75 mg/m

Pindone (83261.html) 200 mg/m 100 mg/m

Platinum (soluble salts, as Pt) (platinum.html) N.E. 4 mg Pt/m

Portland cement (65997151.html) N.E. 5,000 mg/m

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Propane (74986.html) 20,000 ppm

[LEL]

2,100 ppm [LEL]

n-Propyl acetate (109604.html) 8,000 ppm 1,700 ppm

n-Propyl alcohol(71238.html) 4,000 ppm 800 ppm

Propylene dichloride (78875.html) 2,000 ppm 400 ppm

Propylene imine (75558.html) 500 ppm 100 ppm

Propylene oxide (75569.html) 2,000 ppm 400 ppm

n-Propyl nitrate (627134.html) 2,000 ppm 500 ppm

Pyrethrum (8003347.html) 5,000 mg/m 5,000 mg/m

[Unch]

Pyridine (110861.html) 3,600 ppm 1,000 ppm

Quinone (106514.html) 300 mg/m 100 mg/m

Rhodium (metal fume and insoluble compounds, as

Rh)(7440166.html)

N.E. 100 mg Rh/m

Rhodium (soluble compounds, as Rh)(rhodium.html) N.E. 2 mg Rh/m

Ronnel(299843.html) 5,000 mg/m 300 mg/m

Rotenone (83794.html) Unknown 2,500 mg/m

Selenium compounds (as Se)(7782492.html) Unknown 1 mg Se/m

Selenium hexafluoride (7783791.html) 5 ppm 2 ppm

Silica, amorphous (7631869.html) N.E. 3,000 mg/m

Silica, crystalline (respirable dust) N.E.

(14808607.html)

cristobalite/tridymite: (14808607.html)

25 mg/m

(14808607.html)

quartz/tripoli: (14808607.html)

50 mg/m

Silver (metal dust and soluble compounds, as Ag)

(7440224.html)

N.E. 10 mg Ag/m

Soapstone (soapston.html) N.E. 3,000 mg/m

Sodium fluoroacetate (62748.html) 5 mg/m 2.5 mg/m

Sodium hydroxide (1310732.html) 250 mg/m 10 mg/m

Stibine (7803523.html) 40 ppm 5 ppm

Stoddard solvent (8052413.html) 29,500 mg/m 20,000 mg/m

Strychnine (57249.html) 3 mg/m 3 mg/m [Unch]

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3

3 3

3

3

3

3

3

3

3

3 3

3 3

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Styrene (100425.html) 5,000 ppm 700 ppm

Sulfur dioxide (7446095.html) 100 ppm 100 ppm [Unch]

Sulfuric acid (7664939.html) 80 mg/m 15 mg/m

Sulfur monochloride (10025679.html) 10 ppm 5 ppm

Sulfur pentafluoride (5714227.html) 1 ppm 1 ppm [Unch]

Sulfuryl fluoride (2699798.html) 1,000 ppm 200 ppm

2,4,5-T (93765.html) Unknown 250 mg/m

Talc (14807966.html) N.E. 1,000 mg/m

Tantalum (metal and oxide dust, as Ta)(7440257.html) N.E. 2,500 mg Ta/m

TEDP (3689245.html) 35 mg/m 10 mg/m

Tellurium compounds (as Te) (13494809.html) N.E. 25 mg Te/m

Tellurium hexafluoride (7783804.html) 1 ppm 1 ppm [Unch]

TEPP (107493.html) 10 mg/m 5 mg/m

Terphenyl (o, m, p isomers) (26140603.html) Unknown 500 mg/m

1,1,1,2-Tetrachloro 2,2-difluoroethane (76119.html) 15,000 ppm 2,000 ppm

1,1,2,2-Tetrachloro 1,2-difluoroethane (76120.html) 15,000 ppm 2,000 ppm

1,1,2,2-Tetrachloroethane (79345.html) 150 ppm 100 ppm

Tetrachloroethylene (127184.html) 500 ppm 150 ppm

Tetrachloronaphthalene (1335882.html) Unknown Unknown [Unch]

Tetraethyl lead (as Pb)(78002.html) 40 mg Pb/m 40 mg Pb/m

[Unch]

Tetrahydrofuran (109999.html) 20,000 ppm

[LEL]

2,000 ppm [LEL]

Tetramethyl lead (as Pb) (75741.html) 40 mg Pb/m 40 mg Pb/m

[Unch]

Tetramethyl succinonitrile (3333526.html) 5 ppm 5 ppm [Unch]

Tetranitromethane (509148.html) 5 ppm 4 ppm

Tetryl(479458.html) N.E. 750 mg/m

Thallium (soluble compounds, as Tl) (thallium.html) 20 mg Tl/m 15 mg Tl/m

Thiram (137268.html) 1,500 mg/m 100 mg/m

Tin (inorganic compounds, as Sn)(7440315.html) 400 mg Sn/m 100 mg Sn/m

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3

3

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3

3 3

3

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3

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Tin (organic compounds, as Sn)(tin-org.html) Unknown 25 mg Sn/m

Titanium dioxide (13463677.html) N.E. 5,000 mg/m

Toluene (108883.html) 2,000 ppm 500 ppm

Toluene 2,4-diisocyanate (584849.html) 10 ppm 2.5 ppm

o-Toluidine (95534.html) 100 ppm 50 ppm

Tributyl phosphate (126738.html) 125 ppm 30 ppm

1,1,2-Trichloroethane (79005.html) 500 ppm 100 ppm

Trichloroethylene (79016.html) 1,000 ppm 1,000 ppm

[Unch]

Trichloronaphthalene (1321659.html) Unknown Unknown [Unch]

1,2,3-Trichloropropane (96184.html) 1,000 ppm 100 ppm

1,1,2-Trichloro 1,2,2-trifluoroethane (76131.html) 4,500 ppm 2,000 ppm

Triethylamine (121448.html) 1,000 ppm 200 ppm

Trifluorobromomethane (75638.html) 50,000 ppm 40,000 ppm

2,4,6-Trinitrotoluene (118967.html) 1,000 mg/m 500 mg/m

Triorthocresyl phosphate (78308.html) 40 mg/m 40 mg/m [Unch]

Triphenyl phosphate (115866.html) N.E. 1,000 mg/m

Turpentine (8006642.html) 1,500 ppm 800 ppm

Uranium (insoluble compounds, as U)(7440611.html) 30 mg U/m 10 mg U/m

Uranium (soluble compounds, as U)(uranium.html) 20 mg U/m 10 mg U/m

Vanadium dust (vandust.html) 70 mg/m (as

V2O5)

35 mg V/m

Vanadium fume (vanfume.html) 70 mg/m (as

V2O5)

35 mg V/m

Vinyl toluene (25013154.html) 5,000 ppm 400 ppm

Warfarin (81812.html) 350 mg/m 100 mg/m

Xylene (o, m, p isomers) (95476.html) 1,000 ppm 900 ppm

Xylidine (1300738.html) 150 ppm 50 ppm

Yttrium compounds (as Y) (7440655.html) N.E. 500 mg Y/m

Zinc chloride fume (7646857.html) 4,800 mg/m 50 mg/m

Zinc oxide (1314132.html) 2,500 mg/m 500 mg/m

Zirconium compounds (as Zr) (7440677.html) 500 mg Zr/m 25 mg Zr/m

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