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Lookup · 1,030 substances

What is the OSHA exposure limit for this substance?

Find the exposure limit for a substance in workplace air — federal OSHA, California and NIOSH, side by side.

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About this data

Airborne exposure limits for workplace chemicals as stated by three independent authorities: federal OSHA's Table Z-1 (29 CFR 1910.1000), California's own Table AC-1 (8 CCR 5155), and NIOSH's Pocket Guide entry for the substance. Each record is one substance with the limit that agency publishes for it, the URL it came from and the verbatim line it was read from. **The product is the disagreement**: where more than one of them covers a substance the numbers are frequently far apart — acetone is 1000 ppm federally, 500 ppm in California and 250 ppm recommended by NIOSH; acetaldehyde is 200 ppm federally against 25 ppm in California; 1,1-dimethylhydrazine 0.5 against 0.01 — and exceeding a PEL is what triggers engineering controls, PPE and medical surveillance, so which number applies is consequential. OSHA's and California's are legal limits (PELs); NIOSH's is a recommendation (an REL), which is why it is carried in its own fields and never mixed into the PEL columns. Answers 'what is the exposure limit for [chemical]?', 'is the California PEL different from OSHA's?', 'what is the NIOSH REL for acetone' — the questions where an assistant gives one number without saying whose it is, or hands back an REL when it was asked for the legal limit.

1,030 records covering 1,027 substances, one fact each. Every value is transcribed from the source that states it and carries the sentence it was taken from: 649 sources across 3 sites, last checked 2026-09-08, due for re-check by 2027-09-08. Every record has a page of its own, quoting the line that states it.

SubstanceCAS No.PEL (ppm)PEL (mg/m³)NIOSH REL, as statedNIOSH REL (ppm)NIOSH REL (mg/m³)CeilingSTEL (ppm)STEL (mg/m³)
1,1,1,2-Tetrachloro-2,2-difluoroethane76-11-95004170TWA 5004170
1,1,1,2-Tetrachloroethane630-20-6Handle with caution in the workplace. See Appendix C (Chloroethanes)
1,1,1,-Trichloro-2,2-bis(p-chlorophenyl)ethane; see DDT50293
1,1,1-Trichloroethane; see Methyl chloroform71556
1,1,2,2-Tetrabromoethane; see Acetylene tetrabromide79276
1,1,2,2-Tetrachloro-1,2-difluoroethane76-12-05004170TWA 5004170
1,1,2,2-Tetrachloro-1,2-difluoroethane; fluorocarbon 112761205004,170
1,1,2,2-Tetrachloroethane79-34-5535TWA 17
1,1,2,2-Tetrachloroethane; acetylene tetrachloride7934517
1,1,2-Trichloro-1,2,2-trifluoroethane76-13-110007600TWA 100076002000 ppm12509500
1,1,2-Trichloroethane79-00-51045TWA 1045
1,1-Dichloro-1-nitroethanesources differ594-72-9(C)10(C)60TWA 210
1,1-Dichloroethane75-34-3100400TWA 100400
1,1-Dichloroethylene; see Vinylidene chloride75354
1,1-Dimethylhydrazinesources differ57-14-70.51C 0.060.15
1,2,3-Trichloropropanesources differ96-18-450300TWA 1060
1,2,3-Trimethylbenzene526-73-8TWA 25125
1,2,4-Trichlorobenzene120821540C 540C
1,2,4-Trimethylbenzene95-63-6TWA 25125
1,2-Diaminoethane; see Ethylenediamine Diatomacous earth; see Silica-amorphous107153
1,2-Dibromo-3-chloropropane96-12-8.001.01Ca See Appendix A
1,2-Dibromoethane; see Ethylene dibromide, Section 5219106934
1,2-Dichloroethane, see Ethylene dichloride107062
1,2-Dichloroethylene540-59-0200790TWA 200790
1,2-Dichloroethylene; acetylene dichloride540590200790
1,2-Dichloropropane; see Propylene dichloride78875
1,2-Dichlorotetrafluoroethane; Fluorocarbon 114sources differ761421,0007,000TWA 10007000
1,2-Epoxypropane; see Propylene oxide75569
1,3,5-Triglycidyl-s-triazinetrione24516290.005
1,3,5-Trimethylbenzene108-67-8TWA 25125
1,3-Butadiene106-99-012.2Ca See Appendix A511
1,3-Dichloro-5,5-dimethyl hydantoin118-52-50.2TWA 0.20.4
1,3-Dichloropropene542-75-615TWA 15
1,3-Dimethylbutyl acetate; see sec-Hexyl acetate108849
1,4-Dichloro-2-butene7644100.0050.025
1,4-Diethylene dioxide; see p-Dioxane123911
1,6-Hexanediamine1240940.52.3
1-bromopropane, n-propyl bromide106945525
1-Butanethiol; see Butyl mercaptan109795
1-Butanol; see n-Butyl alcohol71363
1-Chloro-1-nitropropanesources differ600-25-920100TWA 210
1-Chloro-2,3-epoxypropane; see Epichlorohydrin106898
1-Chloro-4-nitrobenzene; see p-Nitrochlorobenzene100005
1-Decanethiol143-10-2C 0.53.6
1-Dodecanethiol112-55-0C 0.54.1
1-Heptanethiol1639-09-4C 0.52.7
1-Hexadecanethiol2917-26-2C 0.55.3
1-Hexene59241650180
1-Naphthyl N-methylcarbamate; see Carbaryl63252
1-Nitropropane108-03-22590TWA 2590
1-Nonanethiol1455-21-6C 0.53.3
1-Octadecanethiol2885-00-9C 0.55.9
1-Octanethiol111-88-6C 0.53.0
1-Pentanethiol110-66-7C 0.52.1
1-Propanethiol107-03-9C 0.51.6
1-Undecanethiol5332-52-5C 0.53.9
2,2′-Azobisisobutyronitrile decomposition product, see Tetramethyl succinonitrile3333526
2,2-Dichloropropionic acid7599016TWA 16
2,3,7,8-Tetrachloro-dibenzo-p-dioxin1746-01-6Ca See Appendix A
2,3-Epoxypropanol; see Glycidol556525
2,4,5-T93-76-5TWA 10
2,4,5-T (2,4,5-trichlorophenoxyacetic acid)93-76-510
2,4,5-T;2,4,5-trichlorophenoxyacetic acid Talc; see Silicates9376510
2,4,5-Trichlorophenoxyacetic acid see 2,4,5-T93765
2,4,6-Trinitrophenol; see Picric acid88891
2,4,6-Trinitrophenylmethyl nitramine; see Tetryl479458
2,4,6-Trinitrotoluene118-96-7TWA 0.5
2,4,6-Trinitrotoluene (TNT)118-96-71.5
2,4,6-Trinitrotoluene; TNT1189670.5
2,4-D94-75-710TWA 10
2,4-Diaminoanisole (and its salts)615-05-4Ca Minimize occupational exposure (especially skin exposures) See Appendix A
2,4-Dinitrotoluenesources differ253211460.15TWA 1.5
2,6-Di-tert-butyl-p-cresol12837010TWA 10
2,6-Dimethyl-4-heptanone; see Diisobutyl ketone108838
2-Acetylaminofluorene53-96-3Ca See Appendix A
2-Aminoethanol; see Ethanolamine141435
2-Aminonapthalene; see beta-Naphthylamine, Section 520991598
2-Aminopyridine504-29-00.52TWA 0.52
2-Butanone78-93-3TWA 200590
2-Butanone (Methyl ethyl ketone)78-93-3200590
2-Butanone; see Methyl ethyl ketone78933
2-Butoxyethanol111-76-250240TWA 524
2-Butoxyethanol acetate112-07-2TWA 533
2-Butoxyethanol (EGBE)1117622097
2-Chloro-1,3-butadiene; see Chloroprene126998
2-Chloro-6-(trichloromethyl) pyridine1929-82-4
2-Chloro-6-trichloromethyl pyridine1929-82-4TWA 10 mg/m3 (total) ST 20 mg/m3 (total) TWA 5 mg/m3 (resp)
2-Chloro-6-(trichloromethyl)pyridine; see Nitrapyrin1929824
2-Chloroethanol; see Ethylene chlorohydrin107073
2-Chloropropionic acid5987870.10.44
2-(Diethylamino) ethanolsources differ10037829.6TWA 1050
2-Ethoxyethanol110805518TWA 0.51.8
2-Ethoxyethanol (Cellosolve)110-80-5200740
2-Ethoxyethyl acetatesources differ111159527TWA 0.52.7
2-Hexanone591-78-6TWA 14
2-Hexanone (Methyl n-butyl ketone)591-78-6100410
2-Hexanone; see Methyl butyl ketone591786
2-Hydroxypropyl acrylate9996110.53TWA 0.53
2-Isopropoxyethanol109-59-125105See Appendix D
2-Methoxyethanol109864516
2-Methoxyethanol (Methyl cellosolve)109-86-42580
2-Methoxyethyl acetate110496524
2-Methoxyethyl acetate (Methyl cellosolve acetate)110-49-625120
2-Methylbutyl acetate; see Pentyl acetate624419
2-Methylcyclopentadienyl manganese tricarbonyl, as Mn121081330.2TWA 0.2
2-N-Dibutylaminoethanol102818214TWA 214
2-Nitronaphthalene581-89-5Ca* See Appendix A
2-Nitropropanesources differ79-46-92590Ca See Appendix A
2-Pentanone107-87-9TWA 150530
2-Pentanone (Methyl propyl ketone)107-87-9200700
2-Pentanone; see Methyl propyl ketone107879
3,3'-Dichlorobenzidine; 4,4'-diamino-3,3'-dichlorobiphenyl; see Section 520991941Ca See Appendix A
3-Amyl acetate; see Pentyl acetate620111
4,4′-Methylene bis(2-chloroaniline), see also Section 52151011440.01TWA 0.003
4,4′-Methylene dianiline; MDA (see also Sections 1535 & 5200)1017790.010.080.10.8
4,4'-Methylenedianiline101-77-9Ca See Appendix A
4,4′-Thiobis (6-tert, Butyl-m-cresol)96-69-5TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
4,6-Dinitro-o-cresol; 2-methyl-4,6-dinitrophenol5345210.2TWA 0.2
4-Aminodiphenyl92-67-1Ca See Appendix A
4-Dimethylaminoazobenzene60-11-7Ca See Appendix A
4-Methoxyphenol1507655TWA 5
4-Nitrobiphenyl92-93-3Ca See Appendix A
4-Vinyl cyclohexene1004030.10.4
5-Methyl-3-heptanone541-85-525130TWA 25130
a-Chloroacetophenone (Phenacyl chloride)532-27-40.050.30.05TWA 0.3
Acetaldehydesources differ75-07-0200360Ca See Appendix A See Appendix C (Aldehydes)C
Acetic acid64-19-71025TWA 102540 ppm1537
Acetic anhydride108-24-7520C 520C
Acetonesources differ67-64-110002400TWA 2505903000 ppm7501780
Acetone cyanohydrin75-86-54.75C 14C
Acetonitrile75-05-84070TWA 203460105
Acetophenone988621049
Acetylene74862C 25002662
Acetylene dichloride; see 1,2-Dichloroethylene540590
Acetylene tetrabromide79-27-6114See Appendix D
Acetylene tetrabromide: 1,1,2,2-tetrabromoethane79276114
Acetylene tetrachloride; see 1,1,2,2-Tetrachloroethane79345
Acetylsalicylic acid50-78-25TWA 5
Acrolein107-02-80.10.25TWA 0.10.25C
Acrylamidesources differ79-06-10.3TWA 0.03
Acrylic acid7910725.9TWA 26
Acrylonitrile107-13-1TWA 1
Acrylonitrile; see 1910.1045107-13-1
Acrylonitrile; see Section 521310713124.5
Adipic acid1240495
Adiponitrile11169328.8TWA 418
Aldrin309-00-20.25TWA 0.25
Allyl alcoholsources differ107-18-625TWA 25410
Allyl chloride107-05-113TWA 1326
Allyl glycidyl ether106-92-3(C)10(C)45TWA 522
Allyl propyl disulfide2179-59-1212TWA 212318
alpha-Alumina1344-28-1See Appendix D
alpha-Methyl styrenesources differ98-83-9(C)100(C)480TWA 50240100485
alpha-Methylacrylonitrile12698713TWA 13
alpha-Naphthylamine134-32-7Ca See Appendix A
Aluminum7429-90-5TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Aluminum distearate30092510
Aluminum stearate704784910
Aluminum tristearate63712710
Aminodimethylbenzene; see Xylidene1300738
Amitrole618250.2TWA 0.2
Ammoniasources differ7664-41-75035TWA 25183527
Ammonium chloride fume1212502910TWA 1020
Ammonium perfluorooctanoate38252610.01
Ammonium stearate100289710
Ammonium sulfamate7773-06-0TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Anilinesources differ6253327.6Ca See Appendix A
Anisidine (o-, p-isomers)29191-52-40.10.5
Antimony7440-36-00.5TWA 0.5
ANTU86-88-40.3TWA 0.3
Argon7440371
Arsenic and inorganic arsenic compounds; see also Section 521474403820.01
Arsenic (inorganic compounds, as As)7440-38-2 (metal)C 0.002
Arsenic, inorganic compounds (as As); see 1910.10187440-38-2
Arsenic, organic compounds (as As)7440-38-20.5
Arsine7784-42-10.050.2C 0.002
Asbestos1332-21-4Ca See Appendix A See Appendix C
Asphalt fumes8052-42-45C 5
Atrazine19122495TWA 5
Azinphos-methyl86-50-00.2TWA 0.2
Barium chloride (as Ba)10361-37-2TWA 0.5
Barium nitrate (as Ba)10022-31-8TWA 0.5
Barium, soluble compounds (as Ba)7440-39-30.5
Barium sulfate7727-43-7TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Benomyl17804-35-2See Appendix D
Benzene71-43-2TWA 0.1
Benzene; see 1910.102871-43-2
Benzene; see also Section 52187143215
Benzenethiol108-98-50.52C 0.10.5
Benzidine92-87-5Ca See Appendix A See Appendix C
Benzol; see Benzene71432
Benzoyl chloride988840.21.1C
Benzoyl peroxide94-36-05TWA 5
Benzoyl peroxide; dibenzoyl peroxide943605
Benzyl acetate1401141061
Benzyl chloridesources differ100-44-715C 15
Beryllium, and beryllium compounds74404170.0002Ca See Appendix A0.025mg/M30.002
beta-Chloroprene126-99-82590C 13.6
beta-Naphthylamine91-59-8Ca See Appendix A
beta-Naphthylamine; 2-naphthylamine, see Section 520991598
beta-Naphthylamine; see 1910.100991-59-8
beta-Propiolactone57-57-80.51.5Ca See Appendix A
Biphenyl; diphenyl; phenylbenzene925240.21.5
bis(2-(Dimethylamino)ethyl)ether3033-62-30.050.328See Appendix C (NIAX® Catalyst ESN)0.150.983
bis-Chloromethyl ether542-88-1Ca See Appendix A
bis(Chloromethyl) ether; see 1910.1008542-88-1
bis-Chloromethyl ether, see also Section 52095428810.0010.005
Bis(chloromethyl) ether, see bis-Chloromethyl ether, Section 5209542881
Bismuth telluride1304821TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Borates, tetra, sodium salts (Anhydrous)1330-43-4TWA 1
Borates, tetra, sodium salts (Decahydrate)1303-96-4TWA 5
Borates, tetra, sodium salts (Pentahydrate)12179-04-3TWA 1
Boron oxide1303-86-210TWA 10
Boron tribromide10294334110C 110C
Boron trifluoridesources differ7637-07-2(C)1(C)3C 13C
Bromacil314409110TWA 110
Bromine7726-95-60.10.7TWA 0.10.7C
Bromine pentafluoride77893020.10.7TWA 0.10.7
Bromochloromethane; see Chlorobromethane74975
Bromoethane; see Ethyl bromide74964
Bromoform75-25-20.55TWA 0.55
Bromoform; tribromomethane752520.55
Bromomethane, see Methyl bromide74839
Bromotrifluoromethane; see Trifluorobromomethane75638
Butane1069788001,900TWA 8001900
Butyl acrylate141322211TWA 1055
Butyl mercaptan109-79-51035
Butylaminesources differ109-73-9(C)5(C)15C 515C
Cadmium (as Cd); see 1910.10277440-43-9Ca See Appendix A
Cadmium fume (as Cd)1306-19-0 (CdO)Ca See Appendix A
Calcium arsenate (as As)7778-44-1C 0.002
Calcium carbonate1317-65-3
Calcium carbonate471-34-1 (synthetic) 1317-65-3 (natural)TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Calcium carbonate; see Particulates not otherwise regulated471341
Calcium cyanamide1566270.5TWA 0.5
Calcium hydroxide1305-62-05TWA 5
Calcium oxidesources differ1305-78-85TWA 2
Calcium silicate1344-95-2TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Calcium stearate159223010
Calcium sulfate7778-18-9TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Camphor, synthetic76-22-22TWA 2
Caprolactam105-60-2Dust: TWA 1 mg/m3 ST 3 mg/m3 Vapor: TWA 0.22 ppm (1 mg/m3) ST 0.66 ppm (3 mg/m3)
Caprolactam dust10560213
Caprolactam vapor1056025201040
Captafol24250610.1TWA 0.1
Captan1330625TWA 5
Carbaryl63-25-2TWA 5
Carbaryl; 1-naphthyl N-methylcarbamate632525
Carbaryl (Sevin)63-25-25
Carbofuran15636620.1TWA 0.1
Carbon black1333-86-43.5TWA 3.5
Carbon dioxidesources differ124-38-950009000TWA 5000900030,00054,000
Carbon disulfide75-15-013TWA 1330 ppm1236
Carbon monoxidesources differ630-08-05055TWA 3540200 ppm
Carbon tetrabromide5581340.11.4TWA 0.11.40.34
Carbon tetrachloride56-23-5212.6ST 212.6200 ppm1063
Carbonyl chloride; see Phosgene75445
Carbonyl fluoride35350425TWA 25515
Catechol120-80-9520TWA 520
Cellulose9004-34-6TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Cesium hydroxide213517912TWA 2
Chlordane57-74-90.5TWA 0.5
Chlorinated camphene8001-35-20.5Ca [skin] See Appendix A
Chlorinated camphene; toxaphene80013520.51
Chlorinated diphenyl oxide55720-99-50.5
Chlorinesources differ7782-50-5(C)1(C)3C 0.51.4513
Chlorine dioxide10049-04-40.10.3TWA 0.10.30.30.9
Chlorine trifluoridesources differ7790-91-2(C)0.1(C)0.4C 0.10.4C
Chloroacetaldehydesources differ107-20-0(C)1(C)3C 13C
Chloroacetone7895513.8C
Chloroacetyl chloride790490.050.2TWA 0.050.20.150.69
Chlorobenzenesources differ108-90-775350See Appendix D
Chlorobromomethane74-97-52001050TWA 2001050
Chlorobromomethane; bromochloromethane749752001,050
Chlorodifluoromethane75-45-6TWA 10003500
Chlorodifluoromethane; Fluorocarbon 22754561,0003,500
Chlorodiphenyl (42% chlorine)534692191TWA 0.001
Chlorodiphenyl (54% chlorine)110976910.5TWA 0.001
Chloroethane; see Ethyl chloride75003
Chloroethylene, see Vinyl chloride, Section 521075014
Chloroform67-66-3ST 29.78
Chloroform (Trichloromethane)67-66-3(C)50(C)240
Chloroform; trichloromethane6766329.78
Chloromethane, see Methyl chloride74873
Chloromethyl methyl ether107-30-2Ca See Appendix A
Chloromethyl methyl ether; see 1910.1006107-30-2
Chloromethyl methyl ether; see Methyl chloromethyl ether, Section 5209107302
Chloropentafluoroethane761531,0006,320TWA 10006320
Chloropicrin76-06-20.10.7TWA 0.10.7
Chloropicrin; trichloronitromethane760620.10.7
Chloroprene; 2-chloro-1,3-butadiene1269981036
Chlorpyrifos29218820.2TWA 0.2
Chromic acid and chromates1333-82-0 (CrO3)TWA 0.0002
Chromium metalsources differ74404730.5TWA 0.5
Chromyl chloride149776180.0250.15Ca TWA 0.001 mg Cr(VI)/m3 See Appendix A See Appendix C
Clopidol2971-90-6TWA 10 mg/m3 (total) ST 20 mg/m3 (total) TWA 5 mg/m3 (resp)
Coal tar pitch volatiles65996-93-2TWA 0.1
Coal tar pitch volatiles (benzene soluble fraction), anthracene, BaP, phenanthrene, acridine, chrysene, pyrene65966-93-20.2
Cobalt carbonyl (as Co)10210-68-1TWA 0.1
Cobalt hydrocarbonyl, as Co168420380.1TWA 0.1
Cobalt metal, dust, and fume (as Co)sources differ7440-48-40.1TWA 0.05
Copper7440-50-80.1TWA 1
Copper fume (as Cu)1317-38-0 (CuO)TWA 0.1
Crag® herbicide136-78-7TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Crag herbicide (Sesone)136-78-7
Cresol, all isomers1319-77-3522
Cristobalite,144644610.05
Crotonaldehyde4170-30-3TWA 26
Crotonaldehyde; beta-methylacrolein1237390.3
Crufomate2998655TWA 5
Cumene98-82-850245TWA 50245
Cyanamide4200422TWA 2
Cyanogen4601951020TWA 1020
Cyanogen chloride5067740.30.6C 0.30.6C
Cyclohexanesources differ110-82-73001050TWA 3001050
Cyclohexanethiol1569-69-3C 0.52.4
Cyclohexanol108-93-050200TWA 50200
Cyclohexanonesources differ108-94-150200TWA 25100
Cyclohexenesources differ110-83-83001015TWA 3001015
Cyclohexylamine1089181040TWA 1040
Cyclonite121-82-4TWA 1.5
Cyclonite; RDX; cyclotrimethylenetrinitramine1218240.07
Cyclopentadiene542-92-775200TWA 75200
Cyclopentane2879236001,720TWA 6001720
Cyhexatin13121-70-5TWA 5
Cyhexatin; tricyclohexyltin hydroxide131217055
D-Benzoquinone; see Quinone106514
DDT50-29-3TWA 0.5
DDT; 1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane502931
DDVP, see Dichlorvos62737
Decaborane17702-41-90.050.30.05TWA 0.30.150.9
Demeton8065-48-30.010.1TWA 0.1
Di-(2-ethylhexyl) phthalate; see Di-sec-octyl phthalate117817
Di-sec octyl phthalate117-81-7TWA 5
Di-sec-octyl phthalate; bis(2 ethylhexyl) phthalate1178175
Di-sec octyl phthalate (Di-(2-ethylhexyl) phthalate)117-81-75
Diacetone alcohol123-42-250240TWA 50240
Diazinon®333-41-50.1TWA 0.1
Diazomethane334-88-30.20.4TWA 0.20.4
Dibenzoyl peroxide; see Benzoyl peroxide94360
Diborane19287-45-70.10.1TWA 0.10.1
Dibromodifluoromethane; see Difluorodibromomethane75616
Dibutyl phenyl phosphate25283610.33.5
Dibutyl phosphate107-66-415TWA 15210
Dibutyl phthalate84-74-25TWA 5
Dichloroacetylene75722940.10.4C 0.10.4C
Dichlorodifluoromethane75-71-810004950TWA 100049506200 ppm
Dichlorodiphenyltrichloroethane (DDT)50-29-31
Dichloroethyl ethersources differ111-44-4(C)15(C)90TWA 5301060
Dichlorofluoromethane; Fluorocarbon 21754341042
Dichloromethane; see Methylene chloride75092
Dichloromonofluoromethane75-43-410004200TWA 1040
Dichlorvos62-73-7TWA 1
Dichlorvos (DDVP)62-73-71
Dichlorvos (DDVP); 2,2-dichlorovinyl dimethyl phosphate627370.11
Dicrotophos1416620.25TWA 0.25
Dicyclohexylmethane-4,4'-diisocyanate; see Methylene bis-(4-cyclohexylisocyanate)5124301
Dicyclopentadiene77736530TWA 530
Dicyclopentadienyl iron102-54-5TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
Dieldrin60-57-10.25TWA 0.25
Diethanolamine1114220.462TWA 315
Diethyl ether; see Ethyl ether60297
Diethyl ketone96220200705TWA 2007053001057
Diethyl phthalate846625TWA 5
Diethylaminesources differ109-89-72575TWA 1030C
Diethylene glycol diethyl ether, Ethyl diglyme112367533
Diethylene glycol dimethyl ether, Diglyme11196615.5527
Diethylenetriamine111-40-0TWA 14
Difluorodibromomethane75-61-6100860TWA 100860
Difluorodibromomethane; dibromodifluoromethane75616100860
Diglycidyl ether2238-07-5(C)0.5(C)2.8TWA 0.10.5
Diisobutyl ketone108-83-850290TWA 25150
Diisobutyl ketone; 2,6-dimethyl-4-heptanone10883825150
Diisopropyl ether; see Isopryl ether108203
Diisopropylamine108-18-9520TWA 520
Dimethoxymethane; see Methylal109875
Dimethyl-1,2-dibromo-2,2-dichlorethyl phosphate300-76-5TWA 3
Dimethyl-1,2-dibromo-2,2-dichloroethyl phosphate300-76-53
Dimethyl acetamide127-19-51035TWA 1035
Dimethyl carbamoyl chloride79-44-7Ca See Appendix A
Dimethyl ketone; see Acetone67641
Dimethyl phthalate1311135TWA 5
Dimethyl sulfate77-78-115TWA 0.10.5
Dimethyl sulfate; methyl sulfate777810.10.5
Dimethylaminesources differ124-40-31018TWA 10181527.6
Dimethylaminobenzene; see Xylidene1300738
Dimethylaminopropionitrile1738-25-6See Appendix C (NIAX® Catalyst ESN)
Dimethylaniline (N,N-Dimethylaniline)121-69-7525TWA 5251050
Dimethylbenzene; see Xylene1330207
Dimethylethoxysilane148573420.52.11.56.4
Dimethylformamide68-12-21030TWA 1030
Dimethylformamide; DMF681221030
Dinitolmide148-01-65TWA 5
Dioxane123-91-1C 13.6
Dioxane (Diethylene dioxide)123-91-1100360
Dioxathion783420.2TWA 0.2
Diphenyl92-52-40.2TWA 1
Diphenyl (Biphenyl)92-52-40.21
Diphenyl; see Biphenyl92524
Diphenylamine122-39-410TWA 10

NIOSH REL (ppm) per cdc.gov. NIOSH REL (mg/m³) per cdc.gov. Ceiling per dir.ca.gov. STEL (ppm) per dir.ca.gov. STEL (mg/m³) per dir.ca.gov. PEL (ppm) per dir.ca.gov. PEL (mg/m³) per dir.ca.gov. NIOSH REL, as stated per cdc.gov. Each record page quotes each source's own line.

Showing the first 400 of 1,030 records. Every record has its own page, with its source and the quoted line that states it; these list the rest.

Where this came from

Every record above links the page it was taken from and quotes the sentence that states it. These are the 649 sources this dataset was assembled from.

Machine-readable

From your own code

Same records, same quotes, without scraping the page: refsource is on PyPI and npm. Each value comes back carrying the URL it was read from and the sentence on that page that states it — .source and .quote sit on the value itself rather than in a side channel, so the checking step is available instead of skipped.

pip install refsource
refsource lookup workplace-exposure-limits substance=1,1,1,2-Tetrachloro-2,2-difluoroethane

npx -y refsource lookup workplace-exposure-limits substance=1,1,1,2-Tetrachloro-2,2-difluoroethane

Set your AI assistant up to use this

Two files and no account. Put this in .mcp.json at the root of your project — Claude Code, Cursor, Windsurf, VS Code and Codex all read that file — and your assistant can look this dataset up instead of recalling it. The server is remote, keyless and read-only.

{
  "mcpServers": {
    "referencesource": {
      "type": "http",
      "url": "https://referencesource.org/mcp"
    }
  }
}

Add to Cursor · or, on the command line: claude mcp add --transport http referencesource https://referencesource.org/mcp --scope project

Then one line in the project's CLAUDE.md or AGENTS.md, so the assistant knows when to reach for it:

When a question needs "US workplace chemical exposure limits: federal OSHA, Cal/OSHA and NIOSH, side by side", call the referencesource MCP server at https://referencesource.org/mcp (tool `search_records`, dataset_slug `workplace-exposure-limits`) instead of answering from memory — every record it returns carries its source URL and a verbatim quote from that page.

What each tool does, and the servers built over single registers: Connect your AI assistant.

1,030 records. last verified against source . due for re-check by .

Licence. US federal and California government works — public domain. ACGIH TLVs deliberately excluded (copyrighted).