Original IDLH Value

Substance	Original IDLH Value	Revised IDLH Value
Acetaldehyde	10,000 ppm	2,000 ppm
Acetic acid	1,000 ppm	50 ppm
Acetic anhydride	1,000 ppm	200 ppm
Acetone	20,000 ppm	2,500 ppm [LEL]
Acetonitrile	4,000 ppm	500 ppm
Acetylene tetrabromide	10 ppm	8 ppm
Acrolein	5 ppm	2 ppm
Acrylamide	Unknown	60 mg/m3
Acrylonitrile	500 ppm	85 ppm
Aldrin	100 mg/m3	25 mg/m3
Allyl alcohol	150 ppm	20 ppm
Allyl chloride	300 ppm	250 ppm
Allyl glycidyl ether	270 ppm	50 ppm
2 Aminopyridine	5 ppm	5 ppm [Unch]
Ammonia	500 ppm	300 ppm
Ammonium sulfamate	5,000 mg/m3	1,500 mg/m3
n-Amyl acetate	4,000 ppm	1,000 ppm
sec-Amyl acetate	9,000 ppm	1,000 ppm
Aniline	100 ppm	100 ppm [Unch]
o-Anisidine	50 mg/m3	50 mg/m3 [Unch]
p-Anisidine	50 mg/m3	50 mg/m3 [Unch]
Antimony compounds (as Sb)	80 mg Sb/m3	50 mg Sb/m3
ANTU	100 mg/m3	100 mg/m3 [Unch]
Arsenic (inorganic compounds, as As)	100 mg As/m3	5 mg As/m3
Arsine	6 ppm	3 ppm
Azinphosmethyl	20 mg/m3	10 mg/m3
Barium (soluble compounds, as Ba)	1,100 mg Ba/m3	50 mg Ba/m3
Benzene	3,000 ppm	500 ppm
Benzoyl peroxide	7,000 mg/m3	1,500 mg/m3
Benzyl chloride	10 ppm	10 ppm [Unch]
Beryllium compounds (as Be)	10 mg Be/m3	4 mg Be/m3
Boron oxide	N.E.	2,000 mg/m3
Boron trifluoride	100 ppm	25 ppm
Bromine	10 ppm	3 ppm
Bromoform	Unknown	850 ppm
1,3-Butadiene	20,000 ppm [LEL]	2,000 ppm [LEL]
2-Butanone	3,000 ppm	3,000 ppm [Unch]
2-Butoxyethanol	700 ppm	700 ppm [Unch]
n-Butyl acetate	10,000 ppm	1,700 ppm [LEL]
sec-Butyl acetate	10,000 ppm	1,700 ppm [LEL]
tert-Butyl acetate	10,000 ppm	1,500 ppm [LEL]
n-Butyl alcohol	8,000 ppm	1,400 ppm [LEL]
sec-Butyl alcohol	10,000 ppm	2,000 ppm
tert-Butyl alcohol	8,000 ppm	1,600 ppm
n-Butylamine	2,000 ppm	300 ppm
tert-Butyl chromate	30 mg/m3 (as CrO3)	15 mg Cr(VI)/m3
n-Butyl glycidyl ether	3,500 ppm	250 ppm
n-Butyl mercaptan	2,500 ppm	500 ppm
p-tert-Butyltoluene	1,000 ppm	100 ppm
Cadmium dust (as Cd)	50 mg Cd/m3	9 mg Cd/m3
Cadmium fume (as Cd)	9 mg Cd/m3	9 mg Cd/m3[Unc h]
Calcium arsenate (as As)	100 mg As/m3	5 mg As/m3
Calcium oxide	Unknown	25 mg/m3
Camphor (synthetic)	200 mg/m3	200 mg/m3 [Unch]
Carbaryl	600 mg/m3	100 mg/m3
Carbon black	N.E.	1,750 mg/m3
Carbon dioxide	50,000 ppm	40,000 ppm
Carbon disulfide	500 ppm	500 ppm [Unch]
Carbon monoxide	1,500 ppm	1,200 ppm
Carbon tetrachloride	300 ppm	200 ppm
Chlordane	500 mg/m3	100 mg/m3
Chlorinated camphene	200 mg/m3	200 mg/m3 [Unch]
Chlorinated diphenyl oxide	Unknown	5 mg/m3
Chlorine	30 ppm	10 ppm
Chlorine dioxide	10 ppm	5 ppm
Chlorine trifluoride	20 ppm	20 ppm [Unch]
Chloroacetaldehyde	100 ppm	45 ppm
alpha-Chloroacetophenone	100 mg/m3	15 mg/m3
Chlorobenzene	2,400 ppm	1,000 ppm
o-Chlorobenzylidene malononitrile	2 mg/m3	2 mg/m3 [Unch]
Chlorobromomethane	5,000 ppm	2,000 ppm
Chlorodiphenyl (42% chlorine)	10 mg/m3	5 mg/m3
Chlorodiphenyl (54% chlorine)	5 mg/m3	5 mg/m3 [Unch]
Chloroform	1,000 ppm	500 ppm
1-Chloro-1-nitropropane	2,000 ppm	100 ppm
Chloropicrin	4 ppm	2 ppm
beta-Chloroprene	400 ppm	300 ppm
Chromic acid and chromates	30 mg/m3 (as CrO3)	15 mg Cr(VI)/m3
Chromium (II) compounds [as Cr(II)]	N.E.	250 mg Cr(II)/m3
Chromium (III) compounds [as Cr(III)]	N.E.	25 mg Cr(III)/m3
Chromium metal (as Cr)	N.E.	250 mg Cr/m3
Coal tar pitch volatiles	700 mg/m3	80 mg/m3
Cobalt metal, dust and fume (as Co)	20 mg Co/m3	20 mg Co/m3 [Unch]
Copper (dusts and mists, as Cu)	N.E.	100 mg Cu/m3
Copper fume (as Cu)	N.E.	100 mg Cu/m3
Cotton dust (raw)	N.E.	100 mg/m3
Crag (r) herbicide	5,000 mg/m3	500 mg/m3
Cresol (o, m, p isomers)	250 ppm	250 ppm [Unch]
Crotonaldehyde	400 ppm	50 ppm
Cumene	8,000 ppm	900 ppm [LEL]
Cyanides (as CN)	50 mg/m3 (as CN)	25 mg/m3 (as CN)
Cyclohexane	10,000 ppm	1,300 ppm [LEL]
Cyclohexanol	3,500 ppm	400 ppm
Cyclohexanone	5,000 ppm	700 ppm
Cyclohexene	10,000 ppm	2,000 ppm
Cyclopentadiene	2,000 ppm	750 ppm
2,4-D	500 mg/m3	100 mg/m3
DDT	N.E.	500 mg/m3
Decaborane	100 mg/m3	15 mg/m3
Demeton	20 mg/m3	10 mg/m3
Diacetone alcohol	2,100 ppm	1,800 ppm [LEL]
Diazomethane	2 ppm	2 ppm [Unch]
Diborane	40 ppm	15 ppm
Dibutyl phosphate	125 ppm	30 ppm
Dibutyl phthalate	9,300 mg/m3	4,000 mg/m3
o-Dichlorobenzene	1,000 ppm	200 ppm
p-Dichlorobenzene	1,000 ppm	150 ppm
Dichlorodifluoromethane	50,000 ppm	15,000 ppm
1,3-Dichloro 5,5-dimethylhydantoin	Unknown	5 mg/m3
1,1-Dichloroethane	4,000 ppm	3,000 ppm
1,2-Dichloroethylene	4,000 ppm	1,000 ppm
Dichloroethyl ether	250 ppm	100 ppm
Dichloromonofluoromethane	50,000 ppm	5,000 ppm
1,1-Dichloro 1-nitroethane	150 ppm	25 ppm
Dichlorotetrafluoroethane	50,000 ppm	15,000 ppm
Dichlorvos	200 mg/m3	100 mg/m3
Dieldrin	450 mg/m3	50 mg/m3
Diethylamine	2,000 ppm	200 ppm
2-Diethylaminoethanol	500 ppm	100 ppm
Difluorodibromomethane	2,500 ppm	2,000 ppm
Diglycidyl ether	25 ppm	10 ppm
Diisobutyl ketone	2,000 ppm	500 ppm
Diisopropylamine	1,000 ppm	200 ppm
Dimethyl acetamide	400 ppm	300 ppm
Dimethylamine	2,000 ppm	500 ppm
N,N-Dimethylaniline	100 ppm	100 ppm [Unch]
Dimethyl 1,2-dibromo 2,2-dichlorethyl phosphate	1,800 mg/m3	200 mg/m3
Dimethylformamide	3,500 ppm	500 ppm
1,1-Dimethylhydrazine	50 ppm	15 ppm
Dimethylphthalate	9,300 mg/m3	2,000 mg/m3
Dimethyl sulfate	10 ppm	7 ppm
Dinitrobenzene (o, m, p isomers)	200 mg/m3	50 mg/m3
Dinitroocresol	5 mg/m3	5 mg/m3 [Unch]
Dinitrotoluene	200 mg/m3	50 mg/m3
Di sec-octyl phthalate	Unknown	5,000 mg/m3
Dioxane	2,000 ppm	500 ppm
Diphenyl	300 mg/m3	100 mg/m3
Dipropylene glycol methyl ether	Unknown	600 ppm
Endrin	2,000 mg/m3	2 mg/m3
Epichlorohydrin	250 ppm	75 ppm
EPN	50 mg/m3	5 mg/m3
Ethanolamine	1,000 ppm	30 ppm
2-Ethoxyethanol	6,000 ppm	500 ppm
2-Ethoxyethyl acetate	2,500 ppm	500 ppm
Ethyl acetate	10,000 ppm	2,000 ppm [LEL]
Ethyl acrylate	2,000 ppm	300 ppm
Ethyl alcohol	15,000 ppm	3,300 ppm [LEL]
Ethylamine	4,000 ppm	600 ppm
Ethyl benzene	2,000 ppm	800 ppm [LEL]
Ethyl bromide	3,500 ppm	2,000 ppm
Ethyl butyl ketone	3,000 ppm	1,000 ppm
Ethyl chloride	20,000 ppm	3,800 ppm [LEL]
Ethylene chlorohydrin	10 ppm	7 ppm
Ethylenediamine	2,000 ppm	1,000 ppm
Ethylene dibromide	400 ppm	100 ppm
Ethylene dichloride	1,000 ppm	50 ppm
Ethylene glycol dinitrate	500 mg/m3	75 mg/m3
Ethyleneimine	100 ppm	100 ppm [Unch]
Ethylene oxide	800 ppm	800 ppm [Unch]
Ethyl ether	19,000 ppm [LEL]	1,900 ppm [LEL]
Ethyl formate	8,000 ppm	1,500 ppm
Ethyl mercaptan	2,500 ppm	500 ppm
N-Ethylmorpholine	2,000 ppm	100 ppm
Ethyl silicate	1,000 ppm	700 ppm
Ferbam	N.E.	800 mg/m3
Ferrovanadium dust	N.E.	500 mg/m3
Fluorides (as F)	500 mg F/m3	250 mg F/m3
Fluorine	25 ppm	25 ppm [Unch]
Fluorotrichloromethane	10,000 ppm	2,000 ppm
Formaldehyde	30 ppm	20 ppm
Formic acid	30 ppm	30 ppm [Unch]
Furfural	250 ppm	100 ppm
Furfuryl alcohol	250 ppm	75 ppm
Glycidol	500 ppm	150 ppm
Graphite (natural)	N.E.	1,250 mg/m3
Hafnium compounds (as Hf)	Unknown	50 mg Hf/m3
Heptachlor	700 mg/m3	35 mg/m3
n-Heptane	5,000 ppm	750 ppm
Hexachloroethane	300 ppm	300 ppm [Unch]
Hexachloronaphthalene	2 mg/m3	2 mg/m3 [Unch]
n-Hexane	5,000 ppm	1,100 ppm [LEL]
2-Hexanone	5,000 ppm	1,600 ppm
Hexone	3,000 ppm	500 ppm
sec Hexyl acetate	4,000 ppm	500 ppm
Hydrazine	80 ppm	50 ppm
Hydrogen bromide	50 ppm	30 ppm
Hydrogen chloride	100 ppm	50 ppm
Hydrogen cyanide	50 ppm	50 ppm [Unch]
Hydrogen fluoride (as F)	30 ppm	30 ppm [Unch]
Hydrogen peroxide	75 ppm	75 ppm [Unch]
Hydrogen selenide (as Se)	2 ppm	1 ppm
Hydrogen sulfide	300 ppm	100 ppm
Hydroquinone	Unknown	50 mg/m3
Iodine	10 ppm	2 ppm
Iron oxide dust and fume (as Fe)	N.E.	2,500 mg Fe/m3
Isoamyl acetate	3,000 ppm	1,000 ppm
Isoamyl alcohol (primary and secondary)	10,000 ppm	500 ppm
Isobutyl acetate	7,500 ppm	1,300 ppm [LEL]
Isobutyl alcohol	8,000 ppm	1,600 ppm
Isophorone	800 ppm	200 ppm
Isopropyl acetate	16,000 ppm	1,800 ppm
Isopropyl alcohol	12,000 ppm	2,000 ppm [LEL]
Isopropylamine	4,000 ppm	750 ppm
Isopropyl ether	10,000 ppm	1,400 ppm [LEL]
Isopropyl glycidyl ether	1,000 ppm	400 ppm
Ketene	Unknown	5 ppm
Lead compounds (as Pb)	700 mg Pb/m3	100 mg Pb/m3
Lindane	1,000 mg/m3	50 mg/m3
Lithium hydride	55 mg/m3	0.5 mg/m3
L.P.G.	19,000 ppm [LEL]	2,000 ppm [LEL]
Magnesium oxide fume	N.E.	750 mg/m3
Malathion	5,000 mg/m3	250 mg/m3
Maleic anhydride	Unknown	10 mg/m3
Manganese compounds (as Mn)	N.E.	500 mg Mn/m3
Mercury compounds [except (organo) alkyls, as Hg]	28 mg Hg/m3	10 mg Hg/m3
Mercury (organo) alkyl compounds(as Hg)	10 mg Hg/m3	2 mg Hg/m3
Mesityl oxide	5,000 ppm	1,400 ppm [LEL]
Methoxychlor	N.E.	5,000 mg/m3
Methyl acetate	10,000 ppm	3,100 ppm [LEL]
Methyl acetylene	15,000 ppm [LEL]	1,700 ppm [LEL]
Methyl acetylenepropadiene mixture	15,000 ppm	3,400 ppm [LEL]
Methyl acrylate	1,000 ppm	250 ppm
Methylal	15,000 ppm [LEL]	2,200 ppm [LEL]
Methyl alcohol	25,000 ppm	6,000 ppm
Methylamine	100 ppm	100 ppm [Unch]
Methyl (namyl) ketone	4,000 ppm	800 ppm
Methyl bromide	2,000 ppm	250 ppm
Methyl Cellosolve (r)	2,000 ppm	200 ppm
Methyl Cellosolve (r) acetate	4,000 ppm	200 ppm
Methyl chloride	10,000 ppm	2,000 ppm
Methyl chloroform	1,000 ppm	700 ppm
Methylcyclohexane	10,000 ppm	1,200 ppm [LEL]
Methylcyclohexanol	10,000 ppm	500 ppm
o-Methylcyclohexanone	2,500 ppm	600 ppm
Methylene bisphenyl isocyanate	100 mg/m3	75 mg/m3
Methylene chloride	5,000 ppm	2,300 ppm
Methyl formate	5,000 ppm	4,500 ppm
5-Methyl 3-heptanone	3,000 ppm	100 ppm
Methyl hydrazine	50 ppm	20 ppm
Methyl iodide	800 ppm	100 ppm
Methyl isobutyl carbinol	2,000 ppm	400 ppm
Methyl isocyanate	20 ppm	3 ppm
Methyl mercaptan	400 ppm	150 ppm
Methyl methacrylate	4,000 ppm	1,000 ppm
Methyl styrene	5,000 ppm	700 ppm
Mica	N.E.	1,500 mg/m3
Molybdenum (insoluble compounds, as Mo)	N.E.	5,000 mg Mo/m3
Molybdenum (soluble compounds, as Mo)	N.E.	1,000 mg Mo/m3
Monomethyl aniline	100 ppm	100 ppm [Unch]
Morpholine	8,000 ppm	1,400 ppm [LEL]
Naphtha (coal tar)	10,000 ppm [LEL]	1,000 ppm [LEL]
Naphthalene	500 ppm	250 ppm
Nickel carbonyl (as Ni)	7 ppm	2 ppm
Nickel metal and other compounds (as Ni)	N.E.	10 mg Ni/m3
Nicotine	35 mg/m3	5 mg/m3
Nitric acid	100 ppm	25 ppm
Nitric oxide	100 ppm	100 ppm [Unch]
p-Nitroaniline	300 mg/m3	300 mg/m3 [Unch]
Nitrobenzene	200 ppm	200 ppm [Unch]
p-Nitrochlorobenzene	1,000 mg/m3	100 mg/m3
Nitroethane	1,000 ppm	1,000 ppm [Unch]
Nitrogen dioxide	50 ppm	20 ppm
Nitrogen trifluoride	2,000 ppm	1,000 ppm
Nitroglycerine	500 mg/m3	75 mg/m3
Nitromethane	1,000 ppm	750 ppm
1-Nitropropane	2,300 ppm	1,000 ppm
2-Nitropropane	2,300 ppm	100 ppm
Nitrotoluene (o, m, p isomers)	200 ppm	200 ppm [Unch]
Octachloronaphthalene	Unknown	Unknown [Unch]
Octane	5,000 ppm	1,000 ppm [LEL]
Oil mist (mineral)	N.E.	2,500 mg/m3
Osmium tetroxide (as Os)	1 mg Os/m3	1 mg Os/m3 [Unch]
Oxalic acid	500 mg/m3	500 mg/m3 [Unch]
Oxygen difluoride	0.5 ppm	0.5 ppm [Unch]
Ozone	10 ppm	5 ppm
Paraquat	1.5 mg/m3	1 mg/m3
Parathion	20 mg/m3	10 mg/m3
Pentaborane	3 ppm	1 ppm
Pentachloronaphthalene	Unknown	Unknown [Unch]
Pentachlorophenol	150 mg/m3	2.5 mg/m3
n-Pentane	15,000 ppm [LEL]	1,500 ppm [LEL]
2-Pentanone	5,000 ppm	1,500 ppm
Perchloromethyl mercaptan	10 ppm	10 ppm [Unch]
Perchloryl fluoride	385 ppm	100 ppm
Petroleum distillates (naphtha)	10,000 ppm	1,100 ppm [LEL]
Phenol	250 ppm	250 ppm [Unch]
p-Phenylene diamine	Unknown	25 mg/m3
Phenyl ether (vapor)	N.E.	100 ppm
Phenyl etherbiphenyl mixture (vapor)	N.E.	10 ppm
Phenyl glycidyl ether	Unknown	100 ppm
Phenylhydrazine	295 ppm	15 ppm
Phosdrin	4 ppm	4 ppm [Unch]
Phosgene	2 ppm	2 ppm [Unch]
Phosphine	200 ppm	50 ppm
Phosphoric acid	10,000 mg/m3	1,000 mg/m3
Phosphorus (yellow)	N.E.	5 mg/m3
Phosphorus pentachloride	200 mg/m3	70 mg/m3
Phosphorus pentasulfide	750 mg/m3	250 mg/m3
Phosphorus trichloride	50 ppm	25 ppm
Phthalic anhydride	10,000 mg/m3	60 mg/m3
Picric acid	100 mg/m3	75 mg/m3
Pindone	200 mg/m3	100 mg/m3
Platinum (soluble salts, as Pt)	N.E.	4 mg Pt/m3
Portland cement	N.E.	5,000 mg/m3
Propane	20,000 ppm [LEL]	2,100 ppm [LEL]
n-Propyl acetate	8,000 ppm	1,700 ppm
n-Propyl alcohol	4,000 ppm	800 ppm
Propylene dichloride	2,000 ppm	400 ppm
Propylene imine	500 ppm	100 ppm
Propylene oxide	2,000 ppm	400 ppm
n-Propyl nitrate	2,000 ppm	500 ppm
Pyrethrum	5,000 mg/m3	5,000 mg/m3 [Unch]
Pyridine	3,600 ppm	1,000 ppm
Quinone	300 mg/m3	100 mg/m3
Rhodium (metal fume and insoluble compounds, as Rh)	N.E.	100 mg Rh/m3
Rhodium (soluble compounds, as Rh)	N.E.	2 mg Rh/m3
Ronnel	5,000 mg/m3	300 mg/m3
Rotenone	Unknown	2,500 mg/m3
Selenium compounds (as Se)	Unknown	1 mg Se/m3
Selenium hexafluoride	5 ppm	2 ppm
Silica, amorphous	N.E.	3,000 mg/m3
Silica, crystalline (respirable dust)	N.E.
cristobalite/tridymite:		25 mg/m3
quartz/tripoli:		50 mg/m3
Silver (metal dust and soluble compounds, as Ag)	N.E.	10 mg Ag/m3
Soapstone	N.E.	3,000 mg/m3
Sodium fluoroacetate	5 mg/m3	2.5 mg/m3
Sodium hydroxide	250 mg/m3	10 mg/m3
Stibine	40 ppm	5 ppm
Stoddard solvent	29,500 mg/m3	20,000 mg/m3
Strychnine	3 mg/m3	3 mg/m3 [Unch]
Styrene	5,000 ppm	700 ppm
Sulfur dioxide	100 ppm	100 ppm [Unch]
Sulfuric acid	80 mg/m3	15 mg/m3
Sulfur monochloride	10 ppm	5 ppm
Sulfur pentafluoride	1 ppm	1 ppm [Unch]
Sulfuryl fluoride	1,000 ppm	200 ppm
2,4,5-T	Unknown	250 mg/m3
Talc	N.E.	1,000 mg/m3
Tantalum (metal and oxide dust, as Ta)	N.E.	2,500 mg Ta/m3
TEDP	35 mg/m3	10 mg/m3
Tellurium compounds (as Te)	N.E.	25 mg Te/m3
Tellurium hexafluoride	1 ppm	1 ppm [Unch]
TEPP	10 mg/m3	5 mg/m3
Terphenyl (o, m, p isomers)	Unknown	500 mg/m3
1,1,1,2-Tetrachloro 2,2-difluoroethane	15,000 ppm	2,000 ppm
1,1,2,2-Tetrachloro 1,2-difluoroethane	15,000 ppm	2,000 ppm
1,1,2,2-Tetrachloroethane	150 ppm	100 ppm
Tetrachloroethylene	500 ppm	150 ppm
Tetrachloronaphthalene	Unknown	Unknown [Unch]
Tetraethyl lead (as Pb)	40 mg Pb/m3	40 mg Pb/m3 [Unch]
Tetrahydrofuran	20,000 ppm [LEL]	2,000 ppm [LEL]
Tetramethyl lead (as Pb)	40 mg Pb/m3	40 mg Pb/m3 [Unch]
Tetramethyl succinonitrile	5 ppm	5 ppm [Unch]
Tetranitromethane	5 ppm	4 ppm
Tetryl	N.E.	750 mg/m3
Thallium (soluble compounds, as Tl)	20 mg Tl/m3	15 mg Tl/m3
Thiram	1,500 mg/m3	100 mg/m3
Tin (inorganic compounds, as Sn)	400 mg Sn/m3	100 mg Sn/m3
Tin (organic compounds, as Sn)	Unknown	25 mg Sn/m3
Titanium dioxide	N.E.	5,000 mg/m3
Toluene	2,000 ppm	500 ppm
Toluene 2,4-diisocyanate	10 ppm	2.5 ppm
o-Toluidine	100 ppm	50 ppm
Tributyl phosphate	125 ppm	30 ppm
1,1,2-Trichloroethane	500 ppm	100 ppm
Trichloroethylene	1,000 ppm	1,000 ppm [Unch]
Trichloronaphthalene	Unknown	Unknown [Unch]
1,2,3-Trichloropropane	1,000 ppm	100 ppm
1,1,2-Trichloro 1,2,2-trifluoroethane	4,500 ppm	2,000 ppm
Triethylamine	1,000 ppm	200 ppm
Trifluorobromomethane	50,000 ppm	40,000 ppm
2,4,6-Trinitrotoluene	1,000 mg/m3	500 mg/m3
Triorthocresyl phosphate	40 mg/m3	40 mg/m3 [Unch]
Triphenyl phosphate	N.E.	1,000 mg/m3
Turpentine	1,500 ppm	800 ppm
Uranium (insoluble compounds, as U)	30 mg U/m3	10 mg U/m3
Uranium (soluble compounds, as U)	20 mg U/m3	10 mg U/m3
Vanadium dust	70 mg/m3 (as V2O5)	35 mg V/m3
Vanadium fume	70 mg/m3 (as V2O5)	35 mg V/m3
Vinyl toluene	5,000 ppm	400 ppm
Warfarin	350 mg/m3	100 mg/m3
Xylene (o, m, p isomers)	1,000 ppm	900 ppm
Xylidine	150 ppm	50 ppm
Yttrium compounds (as Y)	N.E.	500 mg Y/m3
Zinc chloride fume	4,800 mg/m3	50 mg/m3
Zinc oxide	2,500 mg/m3	500 mg/m3
Zirconium compounds (as Zr)	500 mg Zr/m3	25 mg Zr/m3