Phosgene

CAS RN: 75-44-5

Hazards Summary

The major hazards encountered in the use and handling of phosgene stem from its toxicologic properties. Toxic by all routes (ie, inhalation, ingestion, and dermal absorption), exposure to this moldy smelling, colorless gas may occur from its use in the manufacture of toluene diisocyanate (TDI), methylenediphenyl diisocyanate (MDI), dyestuffs, polymeric isocyanates, and polycarbonate resins. It is also important to note that certain chlorinated solvents (eg, carbon tetrachloride, chloroform, and methylene chloride) can decompose to phosgene in the presence of fire, heaters, or welding operations. Effects from exposure may include contact burns to the skin and eyes, shortness of breath, chest pain, severe pulmonary edema (sometimes delayed up to 24 hr), and death. Both the OSHA PEL is set at a TWA of 0.1 ppm. Ventilation systems should be used to prevent hazardous levels of phosgene from accumulating. In activities or situations where over-exposure may occur, wear a self-contained breathing apparatus, and full (encapsulating) protective clothing designed specifically to protect against phosgene. If contact should occur, immediately flush the affected skin or eyes with running water for at least 15 minutes. Remove contaminated clothing and shoes at the site. While phosgene does not ignite easily, it can burn, and cylinders may explode in the heat of a fire. For fires involving phosgene, extinguish with dry chemical, CO2, Halon, standard or alcohol foams or water. Fight the fire from a maximum distance and dike runoff from fire control water. Phosgene may be shipped via rail (cargo only), road, and water, in containers bearing the label "Poison gas". Phosgene should be stored in cool, dry, well-ventilated areas, secured, and away from sources of ignition and physical damage. If small leaks of phosgene occur, first isolate the area for 600 feet in all directions (large spills are isolated in all directions for 1200 ft). Stop the flow of gas if it can be done without risk, using water spray to reduce vapor. Sodium hydroxide or anhydrous ammonia have been used to neutralize phosgene. Keep liquid runoff from entering water sources and sewers. Also, gas leaks may be allowed to flow into a mixed solution of caustic soda and slaked lime. Waste phosgene is a potential candidate for rotary kiln or fluidized bed forms of incineration. Before implementing land disposal of waste phosgene, consult with environmental regulatory agencies for guidance.
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