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Regulations (Standards - 29 CFR) - Table of Contents
• Part Number: 1926
• Part Title: Safety and Health Regulations for Construction
• Subpart: D
• Subpart Title: Occupational Health and Environmental Controls
• Standard Number: 1926.55 App A
• Title: Gases, vapors, fumes, dusts, and mists.
• Applicable Standards: 1910.160; 1910.161(a)(2); 1910.162
• GPO Source: e-CFR


NOTE:  Because of the length of the table, explanatory Footnotes applicable to all substances are given 
below as well as at the end of the table.  Footnotes specific only to a limited number of substances are 
also shown within the table.

1 [Reserved]
2 See Mineral Dusts Table.
3 Use Asbestos Limit 1926.58.
4 See 1926.58
* The PELs are 8-hour TWAs unless otherwise noted; a (C)
designation denotes a ceiling limit.
** As determined from breathing-zone air samples.
a Parts of vapor or gas per million parts of contaminated
air by volume at 25 degrees 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 [Reserved]
d 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.
e [Reserved]
f [Reserved]
g For sectors excluded from 1926.1128 the limit is 10 ppm
TWA.
h [Removed]
i [Reserved]
j Millions of particles per cubic foot of air, based on
impinger samples counted by light-field techniques.
k 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.
l [Reserved]
m Covers all organic and inorganic particulates not
otherwise regulated.  Same as Particulates Not Otherwise Regulated.

 The 1970 TLV uses letter designations instead of a numerical value
as follows:

A1 [Reserved]
A2 Polytetrafluoroethylene decomposition products.
Because these products decompose in part by hydrolysis in alkaline
solution, they can be quantitatively determined in air as fluoride to
provide an index of exposure.  No TLV is recommended pending
determination of the toxicity of the products, but air concentrations
should be minimal. 
A3 Gasoline and/or Petroleum distillates.  The composition of 
these materials varies greatly and thus a single TLV for all types of these 
materials is no longer applicable.  The content of benzene, other aromatics
and additives should be determined to arrive at the appropriate TLV.
E Simple asphyxiants.  The limiting factor is the
available oxygen which shall be at least 19.5 percent and be within
the requirements addressing explosion in part 1926.



Appendix A to Sec. 1926.55--1970 American Conference of Governmental 
 Industrial Hygienists' Threshold Limit Values of Airborne Contaminants

                        Threshold Limit Values of Airborne Contaminants for Construction
----------------------------------------------------------------------------------------------------------------
                                                                                        mg/m \3        Skin
                          Substance                              CAS No.\d\    ppm \a\     b\      Designation
----------------------------------------------------------------------------------------------------------------
  Abate; see Temephos........................................
  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 Sec. 1926.1114................         53-96-3
  Acetylene..................................................         74-86-2       E
  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 Sec. 1926.1145........................        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...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Alundum; see alpha-Alumina.................................  ..............
  4-Aminodiphenyl; see Sec. 1926.1111......................         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               --
  Argon......................................................       7440-37-1       E
  Arsenic, inorganic compounds (as As); see Sec. 1926.1118.       7440-38-2      --       --               --
  Arsenic, organic compounds (as As).........................       7440-38-2      --      0.5               --
  Arsine.....................................................       7784-42-1    0.05      0.2               --
  Asbestos; see 1926.58......................................
  Azinphos-methyl............................................         86-50-0      --      0.2                X
  Barium, soluble compounds (as Ba)..........................       7440-39-3      --      0.5               --
  Benzene \g\; see Sec. 1926.1128..........................         71-43-2
  Benzidine; see Sec. 1926.1110............................         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      --    0.002               --
  Biphenyl; see Diphenyl.....................................
  Bisphenol A; see Diglycidyl ether..........................
  Boron oxide................................................       1303-86-2
    Total dust...............................................  ..............      --       15               --
  Boron tribromide...........................................      10294-33-4       1       10               --
  Boron trifluoride..........................................       7637-07-2       (C)1     (C)3            --
  Bromine....................................................       7726-95-6     0.1      0.7               --
  Bromine pentafluoride......................................       7789-30-2     0.1      0.7               --
  Bromoform..................................................         75-25-2     0.5        5                X
  Butadiene (1,3-Butadiene); see 29 CFR 1910.1051; 29 CFR            106-99-0    1 ppm/   .......              --
   1910.19(l)................................................                    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 1926.1126n...............       1189-85-1
  n-Butyl glycidyl ether (BGE)...............................       2426-08-6      50      270               --
  Butyl mercaptan............................................        109-79-5     0.5      1.5               --
  p-tert-Butyltoluene........................................         98-51-1      10       60               --
  Cadmium (as Cd); see 1926.1127.............................       7440-43-9
  Calcium carbonate..........................................       1317-65-3
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Calcium oxide..............................................       1305-78-8      --        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      20       60                X
  Carbon monoxide............................................        630-08-0      50       55               --
  Carbon tetrachloride.......................................         56-23-5      10       65                X
  Cellulose..................................................       9004-34-6
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  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       1        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 Sec. 1926.1108..............        542-88-1
  Chloromethyl methyl ether; see Sec. 1926.1106............        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
  Chromic acid and chromates.................................
    (as CrO3)................................................     Varies with      --      0.1               --
                                                                     compound
  Chromium (II) compounds....................................
    (as Cr)..................................................       7440-47-3      --      0.5               --
  Chromium (III) compounds...................................
    (as Cr)..................................................       7440-47-3      --      0.5               --
  Chromium (VI) compounds see 1926.1126\o\...................
  Chromium metal and insol. salts (as Cr)....................       7440-47-3      --        1               --
  Chrysene; see Coal tar pitch volatiles.....................
  Coal tar pitch volatiles (benzene soluble fraction),             65996-93-2      --      0.2               --
   anthracene, BaP, phenanthrene, acridine, chrysene, pyrene.
  Cobalt metal, dust, and fume (as Co).......................       7440-48-4      --      0.1               --
  Coke oven emissions; see Sec. 1926.1129..................  ..............
  Copper.....................................................       7440-50-8
    Fume (as Cu).............................................  ..............      --      0.1               --
    Dusts and mists (as Cu)..................................  ..............      --        1               --
  Corundum; see Emery........................................
  Cotton dust (raw)..........................................  ..............      --        1
  Crag herbicide (Sesone)....................................        136-78-7
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Cresol, all isomers........................................       1319-77-3       5       22                X
  Crotonaldehyde.............................................       123-73-9;       2        6
                                                                    4170-30-3
  Cumene.....................................................         98-82-8      50      245                X
  Cyanides (as CN)...........................................     Varies with      --        5                X
                                                                     Compound
  Cyanogen...................................................        460-19-5      10       --               --
  Cyclohexane................................................        110-82-7     300     1050               --
  Cyclohexanol...............................................        108-93-0      50      200               --
  Cyclohexanone..............................................        108-94-1      50      200               --
  Cyclohexene................................................        110-83-8     300     1015               --
  Cyclonite..................................................        121-82-4      --      1.5                X
  Cyclopentadiene............................................        542-92-7      75      200               --
  DDT, see Dichlorodiphenyltrichloroethane...................  ..............  .......  .......  ...............
  DDVP, see Dichlorvos.......................................  ..............  .......  .......  ...............
  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 Sec. 1926.1144...         96-12-8  .......  .......              --
  1,2-Dibromoethane; see Ethylene dibromide..................
  Dibutyl phosphate..........................................        107-66-4       1        5               --
  Dibutyl phthalate..........................................         84-74-2      --        5               --
  Dichloroacetylene..........................................       7572-29-4       (C)0.1   (C)0.4          --
  o-Dichlorobenzene..........................................         95-50-1       (C)50    (C)300          --
  p-Dichlorobenzene..........................................        106-46-7      75      450               --
  3,3'-Dichlorobenzidine; see Sec. 1926.1107...............         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
  Dieldrin...................................................         60-57-1      --     0.25                X
  Diethylamine...............................................        109-89-7      25       75               --
  2-Diethylaminoethanol......................................        100-37-8      10       50                X
  Diethylene triamine........................................        111-40-0       (C)10    (C)42            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 Sec. 1926.1115............         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...........................................         77-78-3       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               --
  Diphenylamine..............................................        122-39-4      --       10               --
  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...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Endosulfan.................................................        115-29-7      --      0.1                X
  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.........................
  Ethane.....................................................         74-84-0       E
  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     0.5        1               --
  Ethyl silicate.............................................         78-10-4     100      850               --
  Ethylene...................................................         74-85-1       E
  Ethylene chlorohydrin......................................        107-07-3       5       16                X
  Ethylenediamine............................................        107-15-3      10       25               --
  Ethylene dibromide.........................................        106-93-4       (C)25    (C)190           X
  Ethylene dichloride (1,2-Dichloroethane)...................        107-06-2      50      200               --
  Ethylene glycol dinitrate..................................        628-96-6       (C)0.2   (C)1             X
  Ethylene glycol methyl acetate; see Methyl cellosolve
   acetate...................................................
  Ethyleneimine; see Sec. 1926.1112........................        151-56-4
  Ethylene oxide; see Sec. 1926.1147.......................         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               --
  Fibrous Glass..............................................
    Total dust...............................................  ..............  .......  .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Fluorides (as F)...........................................     Varies with      --      2.5               --
                                                                     compound
  Fluorine...................................................       7782-41-4     0.1      0.2               --
  Fluorotrichloromethane (Trichlorofluoromethane)............         75-69-4    1000     5600               --
  Formaldehyde; see Sec. 1926.1148.........................         50-00-0
  Formic acid................................................         64-18-6       5        9               --
  Furfural...................................................         98-01-1       5       20                X
  Furfuryl alcohol...........................................         98-00-0      50      200               --
  Gasoline...................................................       8006-61-9  .......   A \3\               --
  Glycerin (mist)............................................         56-81-5
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Glycidol...................................................        556-52-5      50      150               --
  Glycol monoethyl ether; see 2-Ethoxyethanol................
  Graphite, natural, respirable dust.........................       7782-42-5   (\2\)    (\2\)            (\2\)
  Graphite, synthetic........................................  ..............
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Guthion; see Azinphos methyl...............................
  Gypsum.....................................................      13397-24-5
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Hafnium....................................................       7440-58-6      --      0.5               --
  Helium.....................................................       7440-59-7       E
  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...................................................       1333-74-0       E
  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       3        2               --
  Hydrogen peroxide..........................................       7722-84-1       1      1.4               --
  Hydrogen selenide (as Se)..................................       7783-07-5    0.05      .02               --
  Hydrogen sulfide...........................................       7783-06-4      10       15               --
  Hydroquinone...............................................        123-31-9      --        2               --
  Indene.....................................................         95-13-6      10       45               --
  Indium and compounds (as In)...............................       7440-74-6      --      0.1               --
  Iodine.....................................................       7553-56-2       (C)0.1   (C)1            --
  Iron oxide fume............................................       1309-37-1      --       10               --
  Iron salts (soluble) (as Fe)...............................     Varies with      --        1               --
                                                                     compound
  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...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Ketene.....................................................        463-51-4     0.5      0.9               --
  Lead, inorganic (as Pb); see 1926.62.......................       7439-92-1
  Limestone..................................................       1317-65-3
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  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...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Magnesium oxide fume.......................................       1309-48-4
    Total particulate........................................  ..............      15       --               --
  Malathion..................................................        121-75-5
    Total dust...............................................  ..............      --       15                X
  Maleic anhydride...........................................        108-31-6    0.25
  Manganese compounds (as Mn)................................       7439-96-5      --        (C)5            --
  Manganese fume (as Mn).....................................       7439-96-5      --        (C)5            --
  Marble.....................................................       1317-65-3
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Mercury (aryl and inorganic)(as Hg)........................       7439-97-6  .......     0.1                X
  Mercury (organo) alkyl compounds (as Hg)...................       7439-97-6      --     0.01                X
  Mercury (vapor) (as Hg)....................................       7439-97-6      --      0.1                X
  Mesityl oxide..............................................        141-79-7      25      100               --
  Methane....................................................         74-82-8       E
  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......
  Methylene chloride; see Sec. 1910.1052...................
  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     500     1740               --
  Methylenedianiline (MDA)...................................        101-77-9  .......  .......  ...............
  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
                                                                                             5
  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     0.5        1               --
  Methyl methacrylate........................................         80-62-6     100      410               --
  Methyl propyl ketone; see 2-Pentanone......................
  Methyl silicate............................................        681-84-5       (C)5     (C)30           --
  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 Sec. 1926.1104..................        134-32-7
  beta-Naphthylamine; see Sec. 1926.1109...................         91-59-8  .......  .......              --
  Neon.......................................................       7440-01-9       E
  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 Sec. 1926.1103......................         92-93-3
  Nitroethane................................................         79-24-3     100      310               --
  Nitrogen...................................................       7727-37-9       E
  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 Sec. 1926.1116...............         62-79-9  .......  .......              --
  Nitrotoluene (all isomers).................................  ..............       5       30                X
    o-isomer.................................................        88-72-2;
    m-isomer.................................................        99-08-1;
    p-isomer.................................................         99-99-0
  Nitrotrichloromethane; see Chloropicrin....................
  Nitrous oxide..............................................      10024-97-2       E
  Octachloronaphthalene......................................       2234-13-1      --      0.1                X
  Octane.....................................................        111-65-9     400     1900               --
  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;      --      0.5                X
                                                                   1910-42-5;
                                                                    2074-50-2
  Parathion..................................................         56-38-2      --      0.1                X
  Particulates not otherwise regulated.......................
    Total dust organic and inorganic.........................  ..............      --       15               --
  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...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Pentane....................................................        109-66-0     500     1500               --
  2-Pentanone (Methyl propyl ketone).........................        107-87-9     200      700               --
  Perchloroethylene (Tetrachloroethylene)....................        127-18-4     100      670               --
  Perchloromethyl mercaptan..................................        594-42-3     0.1      0.8               --
  Perchloryl fluoride........................................       7616-94-6       3     13.5               --
  Petroleum distillates (Naphtha)(Rubber Solvent)............  ..............  .......   A \3\               --
  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               --
  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...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Platinum (as Pt)...........................................       7440-06-4
    Metal....................................................  ..............      --       --               --
    Soluble salts............................................  ..............      --    0.002               --
  Polytetrafluoroethylene decomposition products.............  ..............  .......     A 2
  Portland cement............................................      65997-15-1
    Total dust...............................................  ..............      --       15               --
    Respirable fraction......................................  ..............       5   .......              --
  Propane....................................................         74-98-6       E   .......  ...............
  Propargyl alcohol..........................................        107-19-7       1       --                X
  beta-Propriolactone; see Sec. 1926.1113..................         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      --       10               --
  Rotenone...................................................         83-79-4      --        5               --
  Rouge......................................................  ..............
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  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   (\2\)    (\2\)            (\2\)
  Silica, amorphous, diatomaceous earth, containing less than      61790-53-2   (\2\)    (\2\)            (\2\)
   1% crystalline silica.....................................
  Silica, crystalline cristobalite, respirable dust..........      14464-46-1   (\2\)    (\2\)            (\2\)
  Silica, crystalline quartz, respirable dust................      14808-60-7   (\2\)    (\2\)            (\2\)
  Silica, crystalline tripoli (as quartz), respirable dust...       1317-95-9   (\2\)    (\2\)            (\2\)
  Silica, crystalline tridymite, respirable dust.............      15468-32-3   (\2\)    (\2\)            (\2\)
  Silica, fused, respirable dust.............................      60676-86-0   (\2\)    (\2\)            (\2\)
  Silicates (less than 1% crystalline silica)................
    Mica (respirable dust)...................................      12001-26-2   (\2\)    (\2\)            (\2\)
    Soapstone, total dust....................................  ..............   (\2\)    (\2\)            (\2\)
    Soapstone, respirable dust...............................  ..............   (\2\)    (\2\)            (\2\)
    Talc (containing asbestos); use asbestos limit; see        ..............
     1926.58.................................................
    Talc (containing no asbestos), respirable dust...........      14807-96-6   (\2\)    (\2\)            (\2\)
    Tremolite, asbestiform; see 1926.58......................  ..............
  Silicon carbide............................................        409-21-2
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  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     200     1150               --
  Strychnine.................................................         57-24-9      --     0.15               --
  Styrene....................................................        100-42-5       (C)100   (C)420          --
  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
  Teflon decomposition products..............................  ..............  .......      A2
  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...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  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      --      0.1                X
  Tetrahydrofuran............................................        109-99-9     200      590               --
  Tetramethyl lead, (as Pb)..................................         75-74-1      --     0.15                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
  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               --
  Tin oxide (as Sn)..........................................      21651-19-4      --       --               --
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Titanium dioxide...........................................      13463-67-7
    Total dust...............................................  ..............      --   .......              --
  Toluene....................................................        108-88-3     200      750               --
  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     100      535               --
  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               --
  Trimethyl benzene..........................................      25551-13-7      25      120               --
  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               --
  Tungsten (as W)............................................       7440-33-7
    Insoluble compounds......................................  ..............      --        5               --
    Soluble compounds........................................  ..............      --        1               --
  Turpentine.................................................       8006-64-2     100      560               --
  Uranium (as U).............................................       7440-61-1
    Soluble compounds........................................  ..............      --      0.2               --
    Insoluble compounds......................................  ..............      --      0.2               --
  Vanadium...................................................       1314-62-1
    Respirable dust (as V2 O5)...............................  ..............      --        (C)0.5          --
    Fume (as V2 O5)..........................................  ..............      --        (C)0.1          --
  Vegetable oil mist.........................................  ..............
    Total dust...............................................  ..............      --   .......              --
    Respirable fraction......................................  ..............      --   .......              --
  Vinyl benzene; see Styrene.................................
  Vinyl chloride; see Sec. 1926.1117.......................         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               --
  Zirconium compounds (as Zr)................................       7440-67-7      --        5
----------------------------------------------------------------------------------------------------------------


                                                  Mineral Dusts
SILICA:
  Crystalline
Quartz. Threshold Limit calculated from the formula..............                                        250 (k)
                                                                  ----------------------------------------------
                                                                                                         %SiO2+5

Cristobalite.....................................................
  Amorphous, including natural diatomaceous earth................                                             20
SILICATES (less than 1% crystalline silica)
  Mica...........................................................                                             20
  Portland cement................................................                                             50
  Soapstone......................................................                                             20
  Talc (non-asbestiform).........................................                                             20
  Talc (fibrous), use asbestos limit.............................                                             --

Graphite (natural)...............................................                                             15
----------------------------------------------------------------------------------------------------------------
Inert or Nuisance Particulates: (m)                                 50 (or 15 mg/m3 whichever is the smaller) of
                                                                                             total dust <1% SiO2
[Inert or Nuisance Dusts includes all mineral, inorganic, and
 organic dusts as indicated by examples in TLV's Appendix D]

  Conversion factors.............................................
mppcf x 35.3 = million particles per cubic meter = particles per
 c.c.
----------------------------------------------------------------------------------------------------------------
Footnotes
1 [Reserved]
2 See Mineral Dusts Table.
3 Use Asbestos Limit Sec. 1926.58.
4 See 1926.58.
* The PELs are 8-hour TWAs unless otherwise noted; a (C) designation denotes a ceiling limit.
** As determined from breathing-zone air samples.
a Parts of vapor or gas per million parts of contaminated air by volume at 25 [deg]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 [Reserved]
d 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.
e-f [Reserved]
g For sectors excluded from Sec. 1926.1128 the limit is 10 ppm TWA.
h [Reserved]
i [Reserved]
j Millions of particles per cubic foot of air, based on impinger samples counted by light-field techniques.
k 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.
l [Reserved]
m Covers all organic and inorganic particulates not otherwise regulated. Same as Particulates Not Otherwise
  Regulated.
The 1970 TLV uses letter designations instead of a numerical value as follows:
A1 [Reserved]
A2 Polytetrafluoroethylene decomposition products. Because these products decompose in part by hydrolysis in
  alkaline solution, they can be quantitatively determined in air as fluoride to provide an index of exposure.
  No TLV is recommended pending determination of the toxicity of the products, but air concentrations should be
  minimal.
A3 Gasoline and/or Petroleum Distillates. The composition of these materials varies greatly and thus a single
  TLV for all types of these materials is no longer applicable. The content of benzene, other aromatics and
  additives should be determined to arrive at the appropriate TLV.
E Simple asphyxiants. The limiting factor is the available oxygen which shall be at least 19.5% and be within
  the requirements addressing explosion in part 1926.
  
[39 FR 22801, June 24, 1974, as amended at 51 FR 37007, Oct. 17, 1986; 52 FR 46312, Dec 4, 1987; 58 FR 35089, 
June 30, 1993; 61 FR 9227, March 7, 1996; 61 FR 56746, Nov. 4, 1996; 62 FR 1493, Jan. 10, 1997; 71 FR 10381, Feb. 28, 2006]


Next Standard (1926.56)

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