What are PELs and TLVs


OSHA enforces hundreds of permissible exposure limits (PELs) for toxic air contaminants found in U.S. workplaces. These PELs set enforceable limits on the magnitude and duration of employee exposure to each contaminant. The amount of exposure permitted by a given PEL depends on the toxicity and other characteristics of the particular substance. Two different types of measurement are used for PEL determination. The concentration of gases and liquids in the air is measured in parts per million (ppm). Solids and liquids in the form of mists, dusts, or fumes, are measured in milligrams per cubic meter (mg/m3).
Exposure limits called Threshold Limit Values (TLVs) were developed by the American Conference of Governmental Industral Hygienists (ACGIH). TLVs represent the level of chemicals in the ambient air that most workers can be exposed to on a daily basis without harmful effects.
OSHA’s PELs for air contaminants are located in §1910.1000, Tables Z-1, Z-2, and Z-3. The air contaminant limits were adopted by OSHA in 1971 from existing national consensus standards issued by the American Conference of Governmental Industrial Hygienists and the American National Standards Institute (ANSI). Consequently, these PELs, which have not been updated since 1971, reflect the results of research conducted in the 1950s and 1960s.

Table Z-1: Limits for Air Contaminants
Substance
CAS No. (c)
ppm (a)[a]
mg/m3(b)[a]
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 compound (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
([b])
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 1910.1028d.
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)
7440-41-7
([c])
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
1ppm/5ppm 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 Cr03)
1189-85-1
(C)0.1
X
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
([c])
Carbon monoxide
630-08-0
50
55
Carbon tetrachloride
56-23-5
([c])
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 (Phenacylchloride)
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
Chromic acid and chromates (as CR03)
([b])
([c])
Chromium (II) compounds. (as CR)
7440-47-3
0.5
Chromium (III) compounds. (as CR)
7440-47-3
0.5
Chromium metal and insoluble salts (as CR)
7440-47-3
1
Chrysene; see Coal tarpitch volatiles.
Clopidol
2971-90-6
  • Total dust
15
  • Respirable fraction
5
Coal dust (less than 5% Si02), respirable fraction
([d])
Coal dust (greater than or equal to 5% Si02), respirable fraction
([d])
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 duste, 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)
([b])
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
3,3'-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
([c])
Ethylene dichloride (1,2-Dichloroethane)
107-06-2
([c])
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)
([b])
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
([d])
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
([c])
Hydrogen peroxide
7722-84-1
1
1.4
Hydrogen selenide (as Se)
7783-07-5
0.05
0.2
Hydrogen sulfide
7783-06-4
([c])
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
([c])
Mercury (organo) alkyl compounds (as Hg)
7439-97-6
([c])
Mercury (vapor) (as Hg)
7439-97-6
([c])
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
([c])
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
([c])
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.
Octachioronaphthalene
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
([c])
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, vapors
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-Propiolactone; 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
([d])
Silica, amorphous, diatomaceous earth, containing less than 1% crystalline silica.
61790-53-2
([d])
Silica, crystalline cristobalite, respirable dust
14464-46-1
([d])
Silica, crystalline quartz, respirable dust
14808-60-7
([d])
Silica, crystalline tripoli (as quartz) respirable dust
1317-95-9
([d])
Silica, crystalline tridymite, respirable dust
15468-32-3
([d])
Silica, fused, respirable dust
60676-86-0
([d])
Silicates (less than 1% crystalline silica)
  • Mica (respirable dust)
12001-26-2
([d])
  • Soapstone, total dust
([d])
  • Soapstone, respirable dust
([d])
  • Talc (containing asbestos): use asbestos limit; see 29 CFR 1910.1001.
([d])
  • Talc (containing no asbestos) respirable dust
14807-96-6
([d])
  • 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
([c])
Sucrose
57-50-1
  • Total dust
15
  • Respirable fraction
5
Sulfur dioxide
7446-09-5
5
13
Sulfur hexafluoride
2551-62-4
1000
6000
Sulfur 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-TrinitrophenylmethyInitramine)
479-45-8
1.5
X
Thallium, soluble compounds (as TI)
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
([c])
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
([c])
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-Trinitrophenylmethyl nitramine; 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 V205)
(C)0.5
  • Fume (as V205)
(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
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
[a]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.
  1. Parts of vapor or gas per million parts of contaminated air by volume at 25 °C and 760 torr.
  2. 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.
  3. 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.
  4. 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.
  5. 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 cotton 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.
  6. 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.
[b]Varies with compound.
[c]See Table Z-2.
[d]See Table Z-3.


Table Z-2
Substance
8-hour time weighted average
Acceptable ceiling concentration
Acceptable maximum peak above the acceptable ceiling concentration for an 8-hour shift
Concentration
Maximum duration
Benzene[a] Z37.40-1969
10 ppm
25 ppm
50 ppm
10 minutes.
Beryllium and beryllium compounds (Z37.29-1970)
2 μg/m3
5 μg/m3
25 μg/m3
30 minutes.
Cadmium fume[b] (Z37.5-1970)c
0.1 mg/m3
0.3 mg/m3
Cadmium dust[b] (Z37.5-1970)c
0.2 mg/m3
0.6 mg/m3
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 minutes in any 4 hrs.
Chromic acid and chromates (Z37.7-1971)
1 mg/10m3
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 minutes in any 3 hrs.
Fluoride as dust (Z37.28-1969)
2.5 mg/m3
Formaldehyde; see 1910.1048
Hydrogen fluoride (Z37.28-1969)
3 ppm
Hydrogen sulfide (Z37.1966)
20 ppm
50 ppm
10 mins. once, only if no other meas, exp. occurs.
Mercury (Z37.8-1971)
1 mg/10m3
Methyl chloride (Z37.18-1969)
100 ppm
200 ppm
300 ppm
5 minutes in any 3 hrs.
Methylene chloride: see §1910.1052
Organo (alkyl) mercury (Z37.30-1969)
0.01 mg/m3
0.04 mg/m3
Styrene (Z37.15-1969)
100 ppm
200 ppm
600 ppm
5 minutes in any 3 hrs.
Tetrachloroethylene (Z37.22-1967)
100 ppm
200 ppm
300 ppm
5 minutes 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 minutes 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 §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.

Table Z-3: Mineral Dusts
Substance
Mppcf[a]
mg/m3
Silica:
Crystalline
  • Quartz (Respirable)
250[b]
10 mg/m3e
%SiO2 + 5
%SiO2 + 2
  • Quartz (Total Dust)
30mg/m3
%SiO2 + 2
  • Cristobalite: Use ½ the value calculated from the count or mass formulae for quartz
  • Tridymite: Use ½ the value calculated from the formulae for quartz
Amorphous, including natural diatomaceous earth
20
80 mg/m3
%SiO2
Silicates (less than 1% crystalline silica):
  • Mica
20
  • Soapstone
20
  • Talc (non containing asbestos)
20[c]
  • Talc (containing asbestos). Use asbestos limit.
  • Tremolite (see 29 CFR 1910.1001)
  • Portland cement
50
Graphite (natural)
15
Coal dust:
  • Respirable fraction less than 5% SiO2
2.4 mg/m3e
  • Respirable fraction greater than 5% SiO2
10 mg/m3e
%SiO2+2
Inert or Nuisance Dust:[d]
  • Respirable fraction
15
5mg/m3
  • Total dust
50
15mg/m3
Note 
Conversion factors—mppcf × 35.3 = million particles per cubic meter = particles per c.c.
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 a MRE; the figure corresponding to that of 2.4 mg/m3 in the table for coal dust is 4.5 mg/m3K.
[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 air-borne 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.

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