Appendix IV - Appendix IV to Part 266—Reference Air Concentrations*
| Constituent | CAS No. | RAC (ug/m 3) | Acetaldehyde | 75-07-0 | 10 | Acetonitrile | 75-05-8 | 10 | Acetophenone | 98-86-2 | 100 | Acrolein | 107-02-8 | 20 | Aldicarb | 116-06-3 | 1 | Aluminum Phosphide | 20859-73-8 | 0.3 | Allyl Alcohol | 107-18-6 | 5 | Antimony | 7440-36-0 | 0.3 | Barium | 7440-39-3 | 50 | Barium Cyanide | 542-62-1 | 50 | Bromomethane | 74-83-9 | 0.8 | Calcium Cyanide | 592-01-8 | 30 | Carbon Disulfide | 75-15-0 | 200 | Chloral | 75-87-6 | 2 | Chlorine (free) | 0.4 | 2-Chloro-1,3-butadiene | 126-99-8 | 3 | Chromium III | 16065-83-1 | 1000 | Copper Cyanide | 544-92-3 | 5 | Cresols | 1319-77-3 | 50 | Cumene | 98-82-8 | 1 | Cyanide (free) | 57-12-15 | 20 | Cyanogen | 460-19-5 | 30 | Cyanogen Bromide | 506-68-3 | 80 | Di-n-butyl Phthalate | 84-74-2 | 100 | o-Dichlorobenzene | 95-50-1 | 10 | p-Dichlorobenzene | 106-46-7 | 10 | Dichlorodifluoromethane | 75-71-8 | 200 | 2,4-Dichlorophenol | 120-83-2 | 3 | Diethyl Phthalate | 84-66-2 | 800 | Dimethoate | 60-51-5 | 0.8 | 2,4-Dinitrophenol | 51-28-5 | 2 | Dinoseb | 88-85-7 | 0.9 | Diphenylamine | 122-39-4 | 20 | Endosulfan | 115-29-1 | 0.05 | Endrin | 72-20-8 | 0.3 | Fluorine | 7782-41-4 | 50 | Formic Acid | 64-18-6 | 2000 | Glycidyaldehyde | 765-34-4 | 0.3 | Hexachlorocyclopentadiene | 77-47-4 | 5 | Hexachlorophene | 70-30-4 | 0.3 | Hydrocyanic Acid | 74-90-8 | 20 | Hydrogen Chloride | 7647-01-1 | 7 | Hydrogen Sulfide | 7783-06-4 | 3 | Isobutyl Alcohol | 78-83-1 | 300 | Lead | 7439-92-1 | 0.09 | Maleic Anhydride | 108-31-6 | 100 | Mercury | 7439-97-6 | 0.3 | Methacrylonitrile | 126-98-7 | 0.1 | Methomyl | 16752-77-5 | 20 | Methoxychlor | 72-43-5 | 50 | Methyl Chlorocarbonate | 79-22-1 | 1000 | Methyl Ethyl Ketone | 78-93-3 | 80 | Methyl Parathion | 298-00-0 | 0.3 | Nickel Cyanide | 557-19-7 | 20 | Nitric Oxide | 10102-43-9 | 100 | Nitrobenzene | 98-95-3 | 0.8 | Pentachlorobenzene | 608-93-5 | 0.8 | Pentachlorophenol | 87-86-5 | 30 | Phenol | 108-95-2 | 30 | M-Phenylenediamine | 108-45-2 | 5 | Phenylmercuric Acetate | 62-38-4 | 0.075 | Phosphine | 7803-51-2 | 0.3 | Phthalic Anhydride | 85-44-9 | 2000 | Potassium Cyanide | 151-50-8 | 50 | Potassium Silver Cyanide | 506-61-6 | 200 | Pyridine | 110-86-1 | 1 | Selenious Acid | 7783-60-8 | 3 | Selenourea | 630-10-4 | 5 | Silver | 7440-22-4 | 3 | Silver Cyanide | 506-64-9 | 100 | Sodium Cyanide | 143-33-9 | 30 | Strychnine | 57-24-9 | 0.3 | 1,2,4,5-Tetrachlorobenzene | 95-94-3 | 0.3 | 2,3,4,6-Tetrachlorophenol | 58-90-2 | 30 | Tetraethyl Lead | 78-00-2 | 0.0001 | Tetrahydrofuran | 109-99-9 | 10 | Thallic Oxide | 1314-32-5 | 0.3 | Thallium | 7440-28-0 | 0.5 | Thallium (I) Acetate | 563-68-8 | 0.5 | Thallium (I) Carbonate | 6533-73-9 | 0.3 | Thallium (I) Chloride | 7791-12-0 | 0.3 | Thallium (I) Nitrate | 10102-45-1 | 0.5 | Thallium Selenite | 12039-52-0 | 0.5 | Thallium (I) Sulfate | 7446-18-6 | 0.075 | Thiram | 137-26-8 | 5 | Toluene | 108-88-3 | 300 | 1,2,4-Trichlorobenzene | 120-82-1 | 20 | Trichloromonofluoromethane | 75-69-4 | 300 | 2,4,5-Trichlorophenol | 95-95-4 | 100 | Vanadium Pentoxide | 1314-62-1 | 20 | Warfarin | 81-81-2 | 0.3 | Xylenes | 1330-20-7 | 80 | Zinc Cyanide | 557-21-1 | 50 | Zinc Phosphide | 1314-84-7 | 0.3 |
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*The RAC for other appendix VIII part 261 constituents not listed herein or in appendix V of this part is 0.1 ug/m. 3