29 CFR 1910.1000 - Air contaminants.

Regulations last checked for updates: Dec 19, 2025

Title 29 - Labor last revised: Oct 31, 2025

View all text of Subpart Z [§ 1910.1000 - § 1910.1499]

§ 1910.1000 - Air contaminants.

An employee's exposure to any substance listed in Tables Z-1, Z-2, or Z-3 of this section shall be limited in accordance with the requirements of the following paragraphs of this section.

(a) Table Z-1—(1) Substances with limits preceded by “C”—Ceiling Values. An employee's exposure to any substance in Table Z-1, the exposure limit of which is preceded by a “C”, shall at no time exceed the exposure limit given for that substance. If instantaneous monitoring is not feasible, then the ceiling shall be assessed as a 15-minute time weighted average exposure which shall not be exceeded at any time during the working day.

(2) Other substances—8-hour Time Weighted Averages. An employee's exposure to any substance in Table Z-1, the exposure limit of which is not preceded by a “C”, shall not exceed the 8-hour Time Weighted Average given for that substance in any 8-hour work shift of a 40-hour work week.

(b) Table Z-2. An employee's exposure to any substance listed in Table Z-2 shall not exceed the exposure limits specified as follows:

(1) 8-hour time weighted averages. An employee's exposure to any substance listed in Table Z-2, in any 8-hour work shift of a 40-hour work week, shall not exceed the 8-hour time weighted average limit given for that substance in Table Z-2.

(2) Acceptable ceiling concentrations. An employee's exposure to a substance listed in Table Z-2 shall not exceed at any time during an 8-hour shift the acceptable ceiling concentration limit given for the substance in the table, except for a time period, and up to a concentration not exceeding the maximum duration and concentration allowed in the column under “acceptable maximum peak above the acceptable ceiling concentration for an 8-hour shift.”

(3) Example. During an 8-hour work shift, an employee may be exposed to a concentration of Substance A (with a 10 ppm TWA, 25 ppm ceiling and 50 ppm peak) above 25 ppm (but never above 50 ppm) only for a maximum period of 10 minutes. Such exposure must be compensated by exposures to concentrations less than 10 ppm so that the cumulative exposure for the entire 8-hour work shift does not exceed a weighted average of 10 ppm.

(c) Table Z-3. An employee's exposure to any substance listed in Table Z-3, in any 8-hour work shift of a 40-hour work week, shall not exceed the 8-hour time weighted average limit given for that substance in the table.

(d) Computation formulae. The computation formula which shall apply to employee exposure to more than one substance for which 8-hour time weighted averages are listed in subpart Z of 29 CFR part 1910 in order to determine whether an employee is exposed over the regulatory limit is as follows:

(1)(i) The cumulative exposure for an 8-hour work shift shall be computed as follows:

E = (Ca Ta + Cb Tb + . . .Cn Tn) ÷ 8

Where:

E is the equivalent exposure for the working shift.

C is the concentration during any period of time T where the concentration remains constant.

T is the duration in hours of the exposure at the concentration C.

The value of E shall not exceed the 8-hour time weighted average specified in subpart Z of 29 CFR part 1910 for the substance involved.

(ii) To illustrate the formula prescribed in paragraph (d)(1)(i) of this section, assume that Substance A has an 8-hour time weighted average limit of 100 ppm noted in Table Z-1. Assume that an employee is subject to the following exposure:

Two hours exposure at 150 ppm

Two hours exposure at 75 ppm

Four hours exposure at 50 ppm

Substituting this information in the formula, we have

(2 × 150 + 2 × 75 + 4 × 50) ÷ 8 = 81.25 ppm

Since 81.25 ppm is less than 100 ppm, the 8-hour time weighted average limit, the exposure is acceptable.

(2)(i) In case of a mixture of air contaminants an employer shall compute the equivalent exposure as follows:

Em = (C1 ÷ L1 + C2 ÷ L2) + . . .(Cn ÷ Ln)

Where:

Em is the equivalent exposure for the mixture.

C is the concentration of a particular contaminant.

L is the exposure limit for that substance specified in subpart Z of 29 CFR part 1910.

The value of Em shall not exceed unity (1).

(ii) To illustrate the formula prescribed in paragraph (d)(2)(i) of this section, consider the following exposures:

Substance	Actual concentration of 8-hour exposure (ppm)	8-hour TWA PEL (ppm)
B	500	1,000
C	45	200
D	40	200

Substituting in the formula, we have:

Em = 500 ÷ 1,000 + 45 ÷ 200 + 40 ÷ 200

Em = 0.500 + 0.225 + 0.200

Em = 0.925

Since Em is less than unity (1), the exposure combination is within acceptable limits.

(e) To achieve compliance with paragraphs (a) through (d) of this section, administrative or engineering controls must first be determined and implemented whenever feasible. When such controls are not feasible to achieve full compliance, protective equipment or any other protective measures shall be used to keep the exposure of employees to air contaminants within the limits prescribed in this section. Any equipment and/or technical measures used for this purpose must be approved for each particular use by a competent industrial hygienist or other technically qualified person. Whenever respirators are used, their use shall comply with 1910.134.

Table Z-1—Limits for Air Contaminants

Substance	CAS No. (c)	ppm (a) ¹	mg/m ³ (b) ¹	Skin designation
Acetaldehyde	75-07-0	200	360
Acetic acid	64-19-7	10	25
Acetic anhydride	108-24-7	5	20
Acetone	67-64-1	1000	2400
Acetonitrile	75-05-8	40	70
2-Acetylaminofluorine; see 1910.1014	53-96-3
Acetylene dichloride; see 1,2-Dichloroethylene.
Acetylene tetrabromide	79-27-6	1	14
Acrolein	107-02-8	0.1	0.25
Acrylamide	79-06-1		0.3	X
Acrylonitrile; see 1910.1045	107-13-1
Aldrin	309-00-2		0.25	X
Allyl alcohol	107-18-6	2	5	X
Allyl chloride	107-05-1	1	3
Allyl glycidyl ether (AGE)	106-92-3	(C)10	(C)45
Allyl propyl disulfide	2179-59-1	2	12
alpha-Alumina	1344-28-1
Total dust			15
Respirable fraction			5
Aluminum, metal (as Al)	7429-90-5
Total dust			15
Respirable fraction			5
4-Aminodiphenyl; see 1910.1011	92-67-1
2-Aminoethanol; see Ethanolamine.
2-Aminopyridine	504-29-0	0.5	2
Ammonia	7664-41-7	50	35
Ammonium sulfamate	7773-06-0
Total dust			15
Respirable fraction			5
n-Amyl acetate	628-63-7	100	525
sec-Amyl acetate	626-38-0	125	650
Aniline and homologs	62-53-3	5	19	X
Anisidine (o-, p-isomers)	29191-52-4		0.5	X
Antimony and compounds (as Sb)	7440-36-0		0.5
ANTU (alpha Naphthylthiourea)	86-88-4		0.3
Arsenic, inorganic compounds (as As); see 1910.1018	7440-38-2
Arsenic, organic compounds (as As)	7440-38-2		0.5
Arsine	7784-42-1	0.05	0.2
Asbestos; see 1910.1001	( ⁴)
Azinphos-methyl	86-50-0		0.2	X
Barium, soluble compounds (as Ba)	7440-39-3		0.5
Barium sulfate	7727-43-7
Total dust			15
Respirable fraction			5
Benomyl	17804-35-2
Total dust			15
Respirable fraction			5
Benzene; see 1910.1028	71-43-2
See Table Z-2 for the limits applicable in the operations or sectors excluded in 1910.1028 ^d
Benzidine; see 1910.1010	92-87-5
p-Benzoquinone; see Quinone.
Benzo(a)pyrene; see Coal tar pitch volatiles.
Benzoyl peroxide	94-36-0		5
Benzyl chloride	100-44-7	1	5
Beryllium and beryllium compounds (as Be); see 1926.1124 ⁸	7440-41-7
Biphenyl; see Diphenyl.
Bismuth telluride, Undoped	1304-82-1
Total dust			15
Respirable fraction			5
Boron oxide	1303-86-2
Total dust			15
Boron trifluoride	7637-07-2	(C)1	(C)3
Bromine	7726-95-6	0.1	0.7
Bromoform	75-25-2	0.5	5	X
Butadiene (1,3-Butadiene); See 29 CFR 1910.1051; 29 CFR 1910.19(l)	106-99-0	1 ppm/5 ppm STEL
Butanethiol; see Butyl mercaptan.
2-Butanone (Methyl ethyl ketone)	78-93-3	200	590
2-Butoxyethanol	111-76-2	50	240	X
n-Butyl-acetate	123-86-4	150	710
sec-Butyl acetate	105-46-4	200	950
tert-Butyl acetate	540-88-5	200	950
n-Butyl alcohol	71-36-3	100	300
sec-Butyl alcohol	78-92-2	150	450
tert-Butyl alcohol	75-65-0	100	300
Butylamine	109-73-9	(C)5	(C)15	X
tert-Butyl chromate (as CrO3); see 1910.1026 ⁶	1189-85-1
n-Butyl glycidyl ether (BGE)	2426-08-6	50	270
Butyl mercaptan	109-79-5	10	35
p-tert-Butyltoluene	98-51-1	10	60
Cadmium (as Cd); see 1910.1027	7440-43-9
Calcium carbonate	1317-65-3
Total dust			15
Respirable fraction			5
Calcium hydroxide	1305-62-0
Total dust			15
Respirable fraction			5
Calcium oxide	1305-78-8		5
Calcium silicate	1344-95-2
Total dust			15
Respirable fraction			5
Calcium sulfate	7778-18-9
Total dust			15
Respirable fraction			5
Camphor, synthetic	76-22-2		2
Carbaryl (Sevin)	63-25-2		5
Carbon black	1333-86-4		3.5
Carbon dioxide	124-38-9	5000	9000
Carbon disulfide	75-15-0		( ²)
Carbon monoxide	630-08-0	50	55
Carbon tetrachloride	56-23-5		( ²)
Cellulose	9004-34-6
Total dust			15
Respirable fraction			5
Chlordane	57-74-9		0.5	X
Chlorinated camphene	8001-35-2		0.5	X
Chlorinated diphenyl oxide	55720-99-5		0.5
Chlorine	7782-50-5	(C)1	(C)3
Chlorine dioxide	10049-04-4	0.1	0.3
Chlorine trifluoride	7790-91-2	(C)0.1	(C)0.4
Chloroacetaldehyde	107-20-0	(C)1	(C)3
a-Chloroacetophenone (Phenacyl chloride)	532-27-4	0.05	0.3
Chlorobenzene	108-90-7	75	350
o-Chlorobenzylidene malononitrile	2698-41-1	0.05	0.4
Chlorobromomethane	74-97-5	200	1050
2-Chloro-1,3-butadiene; see beta-Chloroprene.
Chlorodiphenyl (42% Chlorine) (PCB)	53469-21-9		1	X
Chlorodiphenyl (54% Chlorine) (PCB)	11097-69-1		0.5	X
1-Chloro-2,3-epoxypropane; see Epichlorohydrin.
2-Chloroethanol; see Ethylene chlorohydrin.
Chloroethylene; see Vinyl chloride.
Chloroform (Trichloromethane)	67-66-3	(C)50	(C)240
bis(Chloromethyl) ether; see 1910.1008	542-88-1
Chloromethyl methyl ether; see 1910.1006	107-30-2
1-Chloro-1-nitropropane	600-25-9	20	100
Chloropicrin	76-06-2	0.1	0.7
beta-Chloroprene	126-99-8	25	90	X
2-Chloro-6-(trichloromethyl) pyridine	1929-82-4
Total dust			15
Respirable fraction			5
Chromium (II) compounds.
(as Cr)	7440-47-3		0.5
Chromium (III) compounds.
(as Cr)	7440-47-3		0.5
Chromium (VI) compounds; See 1910.1026 ⁵
Chromium metal and insol. salts (as Cr)	7440-47-3		1
Chrysene; see Coal tar pitch volatiles.
Clopidol	2971-90-6
Total dust			15
Respirable fraction			5
Coal dust (less than 5% SiO2), respirable fraction			( ³)
Coal dust (greater than or equal to 5% SiO2), respirable fraction			( ³)
Coal tar pitch volatiles (benzene soluble fraction), anthracene, BaP, phenanthrene, acridine, chrysene, pyrene	65966-93-2		0.2
Cobalt metal, dust, and fume (as Co)	7440-48-4		0.1
Coke oven emissions; see 1910.1029.
Copper	7440-50-8
Fume (as Cu)			0.1
Dusts and mists (as Cu)			1
Cotton dust ^e; see 1910.1043			1
Crag herbicide (Sesone)	136-78-7
Total dust			15
Respirable fraction			5
Cresol, all isomers	1319-77-3	5	22	X
Crotonaldehyde	123-73-9; 4170-30-3	2	6
Cumene	98-82-8	50	245	X
Cyanides (as CN)	( ⁴)		5	X
Cyclohexane	110-82-7	300	1050
Cyclohexanol	108-93-0	50	200
Cyclohexanone	108-94-1	50	200
Cyclohexene	110-83-8	300	1015
Cyclopentadiene	542-92-7	75	200
2,4-D (Dichlorophenoxyacetic acid)	94-75-7		10
Decaborane	17702-41-9	0.05	0.3	X
Demeton (Systox)	8065-48-3		0.1	X
Diacetone alcohol (4-Hydroxy-4-methyl-2-pentanone)	123-42-2	50	240
1,2-Diaminoethane; see Ethylenediamine.
Diazomethane	334-88-3	0.2	0.4
Diborane	19287-45-7	0.1	0.1
1,2-Dibromo-3-chloropropane (DBCP); see 1910.1044	96-12-8
1,2-Dibromoethane; see Ethylene dibromide.
Dibutyl phosphate	107-66-4	1	5
Dibutyl phthalate	84-74-2		5
o-Dichlorobenzene	95-50-1	(C)50	(C)300
p-Dichlorobenzene	106-46-7	75	450
3,′-Dichlorobenzidine; see 1910.1007	91-94-1
Dichlorodifluoromethane	75-71-8	1000	4950
1,3-Dichloro-5,5-dimethyl hydantoin	118-52-5		0.2
Dichlorodiphenyltrichloroethane (DDT)	50-29-3		1	X
1,1-Dichloroethane	75-34-3	100	400
1,2-Dichloroethane; see Ethylene dichloride.
1,2-Dichloroethylene	540-59-0	200	790
Dichloroethyl ether	111-44-4	(C)15	(C)90	X
Dichloromethane; see Methylene chloride.
Dichloromonofluoromethane	75-43-4	1000	4200
1,1-Dichloro-1-nitroethane	594-72-9	(C)10	(C)60
1,2-Dichloropropane; see Propylene dichloride.
Dichlorotetrafluoroethane	76-14-2	1000	7000
Dichlorvos (DDVP)	62-73-7		1	X
Dicyclopentadienyl iron	102-54-5
Total dust			15
Respirable fraction			5
Dieldrin	60-57-1		0.25	X
Diethylamine	109-89-7	25	75
2-Diethylaminoethanol	100-37-8	10	50	X
Diethyl ether; see Ethyl ether.
Difluorodibromomethane	75-61-6	100	860
Diglycidyl ether (DGE)	2238-07-5	(C)0.5	(C)2.8
Dihydroxybenzene; see Hydroquinone.
Diisobutyl ketone	108-83-8	50	290
Diisopropylamine	108-18-9	5	20	X
4-Dimethylaminoazobenzene; see 1910.1015	60-11-7
Dimethoxymethane; see Methylal.
Dimethyl acetamide	127-19-5	10	35	X
Dimethylamine	124-40-3	10	18
Dimethylaminobenzene; see Xylidine
Dimethylaniline (N,N-Dimethylaniline)	121-69-7	5	25	X
Dimethylbenzene; see Xylene.
Dimethyl-1,2-dibromo-2,2-dichloroethyl phosphate	300-76-5		3
Dimethylformamide	68-12-2	10	30	X
2,6-Dimethyl-4-heptanone; see Diisobutyl ketone.
1,1-Dimethylhydrazine	57-14-7	0.5	1	X
Dimethylphthalate	131-11-3		5
Dimethyl sulfate	77-78-1	1	5	X
Dinitrobenzene (all isomers)			1	X
(ortho)	528-29-0
(meta)	99-65-0
(para)	100-25-4
Dinitro-o-cresol	534-52-1		0.2	X
Dinitrotoluene	25321-14-6		1.5	X
Dioxane (Diethylene dioxide)	123-91-1	100	360	X
Diphenyl (Biphenyl)	92-52-4	0.2	1
Diphenylmethane diisocyanate; see Methylene bisphenyl isocyanate.
Dipropylene glycol methyl ether	34590-94-8	100	600	X
Di-sec octyl phthalate (Di-(2-ethylhexyl) phthalate)	117-81-7		5
Emery	12415-34-8
Total dust			15
Respirable fraction			5
Endrin	72-20-8		0.1	X
Epichlorohydrin	106-89-8	5	19	X
EPN	2104-64-5		0.5	X
1,2-Epoxypropane; see Propylene oxide.
2,3-Epoxy-1-propanol; see Glycidol.
Ethanethiol; see Ethyl mercaptan.
Ethanolamine	141-43-5	3	6
2-Ethoxyethanol (Cellosolve)	110-80-5	200	740	X
2-Ethoxyethyl acetate (Cellosolve acetate)	111-15-9	100	540	X
Ethyl acetate	141-78-6	400	1400
Ethyl acrylate	140-88-5	25	100	X
Ethyl alcohol (Ethanol)	64-17-5	1000	1900
Ethylamine	75-04-7	10	18
Ethyl amyl ketone (5-Methyl-3-heptanone)	541-85-5	25	130
Ethyl benzene	100-41-4	100	435
Ethyl bromide	74-96-4	200	890
Ethyl butyl ketone (3-Heptanone)	106-35-4	50	230
Ethyl chloride	75-00-3	1000	2600
Ethyl ether	60-29-7	400	1200
Ethyl formate	109-94-4	100	300
Ethyl mercaptan	75-08-1	(C)10	(C)25
Ethyl silicate	78-10-4	100	850
Ethylene chlorohydrin	107-07-3	5	16	X
Ethylenediamine	107-15-3	10	25
Ethylene dibromide	106-93-4		( ²)
Ethylene dichloride (1,2-Dichloroethane)	107-06-2		( ²)
Ethylene glycol dinitrate	628-96-6	(C)0.2	(C)1	X
Ethylene glycol methyl acetate; see Methyl cellosolve acetate.
Ethyleneimine; see 1910.1012	151-56-4
Ethylene oxide; see 1910.1047	75-21-8
Ethylidene chloride; see 1,1-Dichloroethane.
N-Ethylmorpholine	100-74-3	20	94	X
Ferbam	14484-64-1
Total dust			15
Ferrovanadium dust	12604-58-9		1
Fluorides (as F)	( ⁴)		2.5
Fluorine	7782-41-4	0.1	0.2
Fluorotrichloromethane (Trichlorofluoromethane)	75-69-4	1000	5600
Formaldehyde; see 1910.1048	50-00-0
Formic acid	64-18-6	5	9
Furfural	98-01-1	5	20	X
Furfuryl alcohol	98-00-0	50	200
Grain dust (oat, wheat, barley)			10
Glycerin (mist)	56-81-5
Total dust			15
Respirable fraction			5
Glycidol	556-52-5	50	150
Glycol monoethyl ether; see 2-Ethoxyethanol.
Graphite, natural, respirable dust	7782-42-5		( ³)
Graphite, synthetic
Total dust			15
Respirable fraction			5
Guthion; see Azinphos methyl.
Gypsum	13397-24-5
Total dust			15
Respirable fraction			5
Hafnium	7440-58-6		0.5
Heptachlor	76-44-8		0.5	X
Heptane (n-Heptane)	142-82-5	500	2000
Hexachloroethane	67-72-1	1	10	X
Hexachloronaphthalene	1335-87-1		0.2	X
n-Hexane	110-54-3	500	1800
2-Hexanone (Methyl n-butyl ketone)	591-78-6	100	410
Hexone (Methyl isobutyl ketone)	108-10-1	100	410
sec-Hexyl acetate	108-84-9	50	300
Hydrazine	302-01-2	1	1.3	X
Hydrogen bromide	10035-10-6	3	10
Hydrogen chloride	7647-01-0	(C)5	(C)7
Hydrogen cyanide	74-90-8	10	11	X
Hydrogen fluoride (as F)	7664-39-3		( ²)
Hydrogen peroxide	7722-84-1	1	1.4
Hydrogen selenide (as Se)	7783-07-5	0.05	0.2
Hydrogen sulfide	7783-06-4		( ²)
Hydroquinone	123-31-9		2
Iodine	7553-56-2	(C)0.1	(C)1
Iron oxide fume	1309-37-1		10
Isoamyl acetate	123-92-2	100	525
Isoamyl alcohol (primary and secondary)	123-51-3	100	360
Isobutyl acetate	110-19-0	150	700
Isobutyl alcohol	78-83-1	100	300
Isophorone	78-59-1	25	140
Isopropyl acetate	108-21-4	250	950
Isopropyl alcohol	67-63-0	400	980
Isopropylamine	75-31-0	5	12
Isopropyl ether	108-20-3	500	2100
Isopropyl glycidyl ether (IGE)	4016-14-2	50	240
Kaolin	1332-58-7
Total dust			15
Respirable fraction			5
Ketene	463-51-4	0.5	0.9
Lead, inorganic (as Pb); see 1910.1025	7439-92-1
Limestone	1317-65-3
Total dust			15
Respirable fraction			5
Lindane	58-89-9		0.5	X
Lithium hydride	7580-67-8		0.025
L.P.G. (Liquefied petroleum gas)	68476-85-7	1000	1800
Magnesite	546-93-0
Total dust			15
Respirable fraction			5
Magnesium oxide fume	1309-48-4
Total particulate			15
Malathion	121-75-5
Total dust			15	X
Maleic anhydride	108-31-6	0.25	1
Manganese compounds (as Mn)	7439-96-5		(C)5
Manganese fume (as Mn)	7439-96-5		(C)5
Marble	1317-65-3
Total dust			15
Respirable fraction			5
Mercury (aryl and inorganic) (as Hg)	7439-97-6		( ²)
Mercury (organo) alkyl compounds (as Hg)	7439-97-6		( ²)
Mercury (vapor) (as Hg)	7439-97-6		( ²)
Mesityl oxide	141-79-7	25	100
Methanethiol; see Methyl mercaptan.
Methoxychlor	72-43-5
Total dust			15
2-Methoxyethanol (Methyl cellosolve)	109-86-4	25	80	X
2-Methoxyethyl acetate (Methyl cellosolve acetate)	110-49-6	25	120	X
Methyl acetate	79-20-9	200	610
Methyl acetylene (Propyne)	74-99-7	1000	1650
Methyl acetylene-propadiene mixture (MAPP)		1000	1800
Methyl acrylate	96-33-3	10	35	X
Methylal (Dimethoxy-methane)	109-87-5	1000	3100
Methyl alcohol	67-56-1	200	260
Methylamine	74-89-5	10	12
Methyl amyl alcohol; see Methyl isobutyl carbinol.
Methyl n-amyl ketone	110-43-0	100	465
Methyl bromide	74-83-9	(C)20	(C)80	X
Methyl butyl ketone; see 2-Hexanone.
Methyl cellosolve; see 2-Methoxyethanol.
Methyl cellosolve acetate; see 2-Methoxyethyl acetate.
Methyl chloride	74-87-3		( ²)
Methyl chloroform (1,1,1-Trichloroethane)	71-55-6	350	1900
Methylcyclohexane	108-87-2	500	2000
Methylcyclohexanol	25639-42-3	100	470
o-Methylcyclohexanone	583-60-8	100	460	X
Methylene chloride	75-09-2		( ²)
Methyl ethyl ketone (MEK); see 2-Butanone.
Methyl formate	107-31-3	100	250
Methyl hydrazine (Monomethyl hydrazine)	60-34-4	(C)0.2	(C)0.35	X
Methyl iodide	74-88-4	5	28	X
Methyl isoamyl ketone	110-12-3	100	475
Methyl isobutyl carbinol	108-11-2	25	100	X
Methyl isobutyl ketone; see Hexone.
Methyl isocyanate	624-83-9	0.02	0.05	X
Methyl mercaptan	74-93-1	(C)10	(C)20
Methyl methacrylate	80-62-6	100	410
Methyl propyl ketone; see 2-Pentanone.
alpha-Methyl styrene	98-83-9	(C)100	(C)480
Methylene bisphenyl isocyanate (MDI)	101-68-8	(C)0.02	(C)0.2
Mica; see Silicates.
Molybdenum (as Mo)	7439-98-7
Soluble compounds			5
Insoluble compounds.
Total dust			15
Monomethyl aniline	100-61-8	2	9	X
Monomethyl hydrazine; see Methyl hydrazine.
Morpholine	110-91-8	20	70	X
Naphtha (Coal tar)	8030-30-6	100	400
Naphthalene	91-20-3	10	50
alpha-Naphthylamine; see 1910.1004	134-32-7
beta-Naphthylamine; see 1910.1009	91-59-8
Nickel carbonyl (as Ni)	13463-39-3	0.001	0.007
Nickel, metal and insoluble compounds (as Ni)	7440-02-0		1
Nickel, soluble compounds (as Ni)	7440-02-0		1
Nicotine	54-11-5		0.5	X
Nitric acid	7697-37-2	2	5
Nitric oxide	10102-43-9	25	30
p-Nitroaniline	100-01-6	1	6	X
Nitrobenzene	98-95-3	1	5	X
p-Nitrochlorobenzene	100-00-5		1	X
4-Nitrodiphenyl; see 1910.1003	92-93-3
Nitroethane	79-24-3	100	310
Nitrogen dioxide	10102-44-0	(C)5	(C)9
Nitrogen trifluoride	7783-54-2	10	29
Nitroglycerin	55-63-0	(C)0.2	(C)2	X
Nitromethane	75-52-5	100	250
1-Nitropropane	108-03-2	25	90
2-Nitropropane	79-46-9	25	90
N-Nitrosodimethylamine; see 1910.1016.
Nitrotoluene (all isomers)		5	30	X
o-isomer	88-72-2
m-isomer	99-08-1
p-isomer	99-99-0
Nitrotrichloromethane; see Chloropicrin.
Octachloronaphthalene	2234-13-1		0.1	X
Octane	111-65-9	500	2350
Oil mist, mineral	8012-95-1		5
Osmium tetroxide (as Os)	20816-12-0		0.002
Oxalic acid	144-62-7		1
Oxygen difluoride	7783-41-7	0.05	0.1
Ozone	10028-15-6	0.1	0.2
Paraquat, respirable dust	4685-14-7; 1910-42-5; 2074-50-2		0.5	X
Parathion	56-38-2		0.1	X
Particulates not otherwise regulated (PNOR) ^f.
Total dust			15
Respirable fraction			5
PCB; see Chlorodiphenyl (42% and 54% chlorine).
Pentaborane	19624-22-7	0.005	0.01
Pentachloronaphthalene	1321-64-8		0.5	X
Pentachlorophenol	87-86-5		0.5	X
Pentaerythritol	115-77-5
Total dust			15
Respirable fraction			5
Pentane	109-66-0	1000	2950
2-Pentanone (Methyl propyl ketone)	107-87-9	200	700
Perchloroethylene (Tetrachloroethylene)	127-18-4		( ²)
Perchloromethyl mercaptan	594-42-3	0.1	0.8
Perchloryl fluoride	7616-94-6	3	13.5
Petroleum distillates (Naphtha) (Rubber Solvent)		500	2000
Phenol	108-95-2	5	19	X
p-Phenylene diamine	106-50-3		0.1	X
Phenyl ether, vapor	101-84-8	1	7
Phenyl ether-biphenyl mixture, vapor		1	7
Phenylethylene; see Styrene.
Phenyl glycidyl ether (PGE)	122-60-1	10	60
Phenylhydrazine	100-63-0	5	22	X
Phosdrin (Mevinphos)	7786-34-7		0.1	X
Phosgene (Carbonyl chloride)	75-44-5	0.1	0.4
Phosphine	7803-51-2	0.3	0.4
Phosphoric acid	7664-38-2		1
Phosphorus (yellow)	7723-14-0		0.1
Phosphorus pentachloride	10026-13-8		1
Phosphorus pentasulfide	1314-80-3		1
Phosphorus trichloride	7719-12-2	0.5	3
Phthalic anhydride	85-44-9	2	12
Picloram	1918-02-1
Total dust			15
Respirable fraction			5
Picric acid	88-89-1		0.1	X
Pindone (2-Pivalyl-1,3-indandione)	83-26-1		0.1
Plaster of Paris	26499-65-0
Total dust			15
Respirable fraction			5
Platinum (as Pt)	7440-06-4
Metal
Soluble salts			0.002
Portland cement	65997-15-1
Total dust			15
Respirable fraction			5
Propane	74-98-6	1000	1800
beta-Propriolactone; see 1910.1013	57-57-8
n-Propyl acetate	109-60-4	200	840
n-Propyl alcohol	71-23-8	200	500
n-Propyl nitrate	627-13-4	25	110
Propylene dichloride	78-87-5	75	350
Propylene imine	75-55-8	2	5	X
Propylene oxide	75-56-9	100	240
Propyne; see Methyl acetylene.
Pyrethrum	8003-34-7		5
Pyridine	110-86-1	5	15
Quinone	106-51-4	0.1	0.4
RDX; see Cyclonite.
Rhodium (as Rh), metal fume and insoluble compounds	7440-16-6		0.1
Rhodium (as Rh), soluble compounds	7440-16-6		0.001
Ronnel	299-84-3		15
Rotenone	83-79-4		5
Rouge
Total dust			15
Respirable fraction			5
Selenium compounds (as Se)	7782-49-2		0.2
Selenium hexafluoride (as Se)	7783-79-1	0.05	0.4
Silica, amorphous, precipitated and gel	112926-00-8		( ³)
Silica, amorphous, diatomaceous earth, containing less than 1% crystalline silica	61790-53-2		( ³)
Silica, crystalline, respirable dust
Cristobalite; see 1910.1053 ⁷	14464-46-1
Quartz; see 1910.1053 ⁷	14808-60-7
Tripoli (as quartz); see 1910.1053 ⁷	1317-95-9
Tridymite; see 1910.1053 ⁷	15468-32-3
Silica, fused, respirable dust	60676-86-0		( ³)
Silicates (less than 1% crystalline silica)
Mica (respirable dust)	12001-26-2		( ³)
Soapstone, total dust			( ³)
Soapstone, respirable dust			( ³)
Talc (containing asbestos); use asbestos limit; see 29 CFR 1910.1001			( ³)
Talc (containing no asbestos), respirable dust	14807-96-6		( ³)
Tremolite, asbestiform; see 1910.1001.
Silicon	7440-21-3
Total dust			15
Respirable fraction			5
Silicon carbide	409-21-2
Total dust			15
Respirable fraction			5
Silver, metal and soluble compounds (as Ag)	7440-22-4		0.01
Soapstone; see Silicates.
Sodium fluoroacetate	62-74-8		0.05	X
Sodium hydroxide	1310-73-2		2
Starch	9005-25-8
Total dust			15
Respirable fraction			5
Stibine	7803-52-3	0.1	0.5
Stoddard solvent	8052-41-3	500	2900
Strychnine	57-24-9		0.15
Styrene	100-42-5		( ²)
Sucrose	57-50-1
Total dust			15
Respirable fraction			5
Sulfur dioxide	7446-09-5	5	13
Sulfur hexafluoride	2551-62-4	1000	6000
Sulfuric acid	7664-93-9		1
Sulfur monochloride	10025-67-9	1	6
Sulfur pentafluoride	5714-22-7	0.025	0.25
Sulfuryl fluoride	2699-79-8	5	20
Systox; see Demeton.
2,4,5-T (2,4,5-trichlorophenoxyacetic acid)	93-76-5		10
Talc; see Silicates.
Tantalum, metal and oxide dust	7440-25-7		5
TEDP (Sulfotep)	3689-24-5		0.2	X
Tellurium and compounds (as Te)	13494-80-9		0.1
Tellurium hexafluoride (as Te)	7783-80-4	0.02	0.2
Temephos	3383-96-8
Total dust			15
Respirable fraction			5
TEPP (Tetraethyl pyrophosphate)	107-49-3		0.05	X
Terphenyls	26140-60-3	(C)1	(C)9
1,1,1,2-Tetrachloro-2,2-difluoroethane	76-11-9	500	4170
1,1,2,2-Tetrachloro-1,2-difluoroethane	76-12-0	500	4170
1,1,2,2-Tetrachloroethane	79-34-5	5	35	X
Tetrachloroethylene; see Perchloroethylene.
Tetrachloromethane; see Carbon tetrachloride.
Tetrachloronaphthalene	1335-88-2		2	X
Tetraethyl lead (as Pb)	78-00-2		0.075	X
Tetrahydrofuran	109-99-9	200	590
Tetramethyl lead (as Pb)	75-74-1		0.075	X
Tetramethyl succinonitrile	3333-52-6	0.5	3	X
Tetranitromethane	509-14-8	1	8
Tetryl (2,4,6-Trinitrophenylmethylnitramine)	479-45-8		1.5	X
Thallium, soluble compounds (as Tl)	7440-28-0		0.1	X
4,4′-Thiobis (6-tert, Butyl-m-cresol)	96-69-5
Total dust			15
Respirable fraction			5
Thiram	137-26-8		5
Tin, inorganic compounds (except oxides) (as Sn)	7440-31-5		2
Tin, organic compounds (as Sn)	7440-31-5		0.1
Titanium dioxide	13463-67-7
Total dust			15
Toluene	108-88-3		( ²)
Toluene-2,4-diisocyanate (TDI)	584-84-9	(C)0.02	(C)0.14
o-Toluidine	95-53-4	5	22	X
Toxaphene; see Chlorinated camphene.
Tremolite; see Silicates.
Tributyl phosphate	126-73-8		5
1,1,1-Trichloroethane; see Methyl chloroform.
1,1,2-Trichloroethane	79-00-5	10	45	X
Trichloroethylene	79-01-6		( ²)
Trichloromethane; see Chloroform.
Trichloronaphthalene	1321-65-9		5	X
1,2,3-Trichloropropane	96-18-4	50	300
1,1,2-Trichloro-1,2,2-trifluoroethane	76-13-1	1000	7600
Triethylamine	121-44-8	25	100
Trifluorobromomethane	75-63-8	1000	6100
2,4,6-Trinitrophenol; see Picric acid.
2,4,6-Trinitrophenylmethylnitramine; see Tetryl.
2,4,6-Trinitrotoluene (TNT)	118-96-7		1.5	X
Triorthocresyl phosphate	78-30-8		0.1
Triphenyl phosphate	115-86-6		3
Turpentine	8006-64-2	100	560
Uranium (as U)	7440-61-1
Soluble compounds			0.05
Insoluble compounds			0.25
Vanadium	1314-62-1
Respirable dust (as V2 O5)			(C)0.5
Fume (as V2 O5)			(C)0.1
Vegetable oil mist
Total dust			15
Respirable fraction			5
Vinyl benzene; see Styrene.
Vinyl chloride; see 1910.1017	75-01-4
Vinyl cyanide; see Acrylonitrile.
Vinyl toluene	25013-15-4	100	480
Warfarin	81-81-2		0.1
Xylenes (o-, m-, p-isomers)	1330-20-7	100	435
Xylidine	1300-73-8	5	25	X
Yttrium	7440-65-5		1
Zinc chloride fume	7646-85-7		1
Zinc oxide fume	1314-13-2		5
Zinc oxide	1314-13-2
Total dust			15
Respirable fraction			5
Zinc stearate	557-05-1
Total dust			15
Respirable fraction			5
Zirconium compounds (as Zr)	7440-67-7		5

¹ The PELs are 8-hour TWAs unless otherwise noted; a (C) designation denotes a ceiling limit. They are to be determined from breathing-zone air samples.

(a) Parts of vapor or gas per million parts of contaminated air by volume at 25 °C and 760 torr.

(b) Milligrams of substance per cubic meter of air. When entry is in this column only, the value is exact; when listed with a ppm entry, it is approximate.

(c) The CAS number is for information only. Enforcement is based on the substance name. For an entry covering more than one metal compound, measured as the metal, the CAS number for the metal is given—not CAS numbers for the individual compounds.

(d) The final benzene standard in 1910.1028 applies to all occupational exposures to benzene except in some circumstances the distribution and sale of fuels, sealed containers and pipelines, coke production, oil and gas drilling and production, natural gas processing, and the percentage exclusion for liquid mixtures; for the excepted subsegments, the benzene limits in Table Z-2 apply. See 1910.1028 for specific circumstances.

(e) This 8-hour TWA applies to respirable dust as measured by a vertical elutriator cotton dust sampler or equivalent instrument. The time-weighted average applies to the cottom waste processing operations of waste recycling (sorting, blending, cleaning and willowing) and garnetting. See also 1910.1043 for cotton dust limits applicable to other sectors.

(f) All inert or nuisance dusts, whether mineral, inorganic, or organic, not listed specifically by substance name are covered by the Particulates Not Otherwise Regulated (PNOR) limit which is the same as the inert or nuisance dust limit of Table Z-3.

² See Table Z-2.

³ See Table Z-3.

⁴ Varies with compound.

⁵ See Table Z-2 for the exposure limit for any operations or sectors where the exposure limit in § 1910.1026 is stayed or is otherwise not in effect.

⁶ If the exposure limit in § 1910.1026 is stayed or is otherwise not in effect, the exposure limit is a ceiling of 0.1 mg/m ³.

⁷ See Table Z-3 for the exposure limit for any operations or sectors where the exposure limit in § 1910.1053 is stayed or is otherwise not in effect.

⁸ See Table Z-2 for the exposure limits for any operations or sectors where the exposure limits in § 1910.1024 are stayed or otherwise not in effect.

Table Z-2

Substance	8-hour time weighted average	Acceptable ceiling concentration	Acceptable maximum peak above the acceptable ceiling concentration for an 8-hr shift
Substance	8-hour time weighted average	Acceptable ceiling concentration	Concentration	Maximum duration
Benzene ^a (Z37.40-1969)	10 ppm	25 ppm	50 ppm	10 minutes.
Beryllium and beryllium compounds (Z37.29-1970) ^d	2 µg/m ³	5 µg/m ³	25 µg/m ³	30 minutes.
Cadmium fume ^b (Z37.5-1970)	0.1 mg/m ³	0.3 mg/m ³
Cadmium dust ^b (Z37.5-1970)	0.2 mg/m ³	0.6 mg/m ³
Carbon disulfide (Z37.3-1968)	20 ppm	30 ppm	100 ppm	30 minutes.
Carbon tetrachloride (Z37.17-1967)	10 ppm	25 ppm	200 ppm	5 min. in any 4 hrs.
Chromic acid and chromates (Z37.7-1971) (as CrO3) ^c		1 mg/10m ³
Ethylene dibromide (Z37.31-1970)	20 ppm	30 ppm	50 ppm	5 minutes.
Ethylene dichloride (Z37.21-1969)	50 ppm	100 ppm	200 ppm	5 min. in any 3 hrs.
Fluoride as dust (Z37.28-1969)	2.5 mg/m ³
Formaldehyde; see 1910.1048
Hydrogen fluoride (Z37.28-1969)	3 ppm
Hydrogen sulfide (Z37.2-1966)		20 ppm	50 ppm	10 mins. once, only if no other meas. exp. occurs.
Mercury (Z37.8-1971)		1 mg/10m ³
Methyl chloride (Z37.18-1969)	100 ppm	200 ppm	300 ppm	5 mins. in any 3 hrs.
Methylene Chloride: See § 1919.52.
Organo (alkyl) mercury (Z37.30-1969)	0.01 mg/m ³	0.04 mg/m ³
Styrene (Z37.15-1969)	100 ppm	200 ppm	600 ppm	5 mins. in any 3 hrs.
Tetrachloroethylene (Z37.22-1967)	100 ppm	200 ppm	300 ppm	5 mins. in any 3 hrs.
Toluene (Z37.12-1967)	200 ppm	300 ppm	500 ppm	10 minutes.
Trichloroethylene (Z37.19-1967)	100 ppm	200 ppm	300 ppm	5 mins. in any 2 hrs.

^a This standard applies to the industry segments exempt from the 1 ppm 8-hour TWA and 5 ppm STEL of the benzene standard at 1910.1028.

^b This standard applies to any operations or sectors for which the Cadmium standard, 1910.1027, is stayed or otherwise not in effect.

^c This standard applies to any operations or sectors for which the exposure limit in the Chromium (VI) standard, § 1910.1026, is stayed or is otherwise not in effect.

^d This standard applies to any operations or sectors for which the exposure limits in the beryllium standard, § 1910.1024, are stayed or is otherwise not in effect.

Table Z-3—Mineral Dusts

Substance	mppcf ^a	mg/m ³
Silica:
Crystalline
Quartz (Respirable) ^f	250 ^b	10 mg/m ³ ^e
	% SiO2 + 5	% SiO2 + 2
Cristobalite: Use 1/2 the value calculated from the count or mass formulae for quartz ^f
Tridymite: Use 1/2 the value calculated from the formulae for quartz ^f

Amorphous, including natural diatomaceous earth	20	80 mg/m ³
		%SiO2

Silicates (less than 1% crystalline silica):
Mica	20
Soapstone	20
Talc (not containing asbestos)	20 ^c
Talc (containing asbestos) Use asbestos limit
Tremolite, asbestiform (see 29 CFR 1910.1001)
Portland cement	50
Graphite (Natural)	15
Coal Dust:

Respirable fraction less than 5% SiO2		2.4 mg/m ³ ^e

		10 mg/m ³ ^e
Respirable fraction greater than 5% SiO2		_____ %SiO2 + 2

Inert or Nuisance Dust: ^d
Respirable fraction	15	5 mg/m ³
Total dust	50	15 mg/m ³

Note—Conversion factors - mppcf × 35.3 = million particles per cubic meter = particles per c.c.

^a Millions of particles per cubic foot of air, based on impinger samples counted by light-field techniques.

^b The percentage of crystalline silica in the formula is the amount determined from airborne samples, except in those instances in which other methods have been shown to be applicable.

^c Containing less than 1% quartz; if 1% quartz or more, use quartz limit.

^d All inert or nuisance dusts, whether mineral, inorganic, or organic, not listed specifically by substance name are covered by this limit, which is the same as the Particulates Not Otherwise Regulated (PNOR) limit in Table Z-1.

^e Both concentration and percent quartz for the application of this limit are to be determined from the fraction passing a size-selector with the following characteristics:

Aerodynamic diameter (unit density sphere)	Percent passing selector
2	90
2.5	75
3.5	50
5.0	25
10	0

The measurements under this note refer to the use of an AEC (now NRC) instrument. The respirable fraction of coal dust is determined with an MRE; the figure corresponding to that of 2.4 mg/m ³ in the table for coal dust is 4.5 mg/m ^3K.

^f This standard applies to any operations or sectors for which the respirable crystalline silica standard, 1910.1053, is stayed or is otherwise not in effect.

[58 FR 35340, June 30, 1993; 58 FR 40191, July 27, 1993, as amended at 61 FR 56831, Nov. 4, 1996; 62 FR 1600, Jan. 10, 1997; 62 FR 42018, Aug. 4, 1997; 71 FR 10373, Feb. 28, 2006; 71 FR 16673, Apr. 3, 2006; 71 FR 36008, June 23, 2006; 81 FR 16861, Mar. 25, 2016; 81 FR 31167, May 18, 2016; 81 FR 60272, Sept. 1, 2016; 82 FR 2735, Jan. 9, 2017]

cite as: 29 CFR 1910.1000