Unknown plant de-construction hazard -- Toxic COS and CS2 gas from torch cutting of pipe

An employee exhibited signs of illness after apparently inhaling fumes generated from a pipe that had been cut with a cutting torch. Identification and quantification of the hazardous air emission for reduction of risk via the Department of Energy Class B Investigation are described in this case study. The old hydrogen sulfide gas flare pipe in the heavy water plant of the Savannah River Site has been abandoned with one end open to atmosphere for almost twenty years. The pipe was being removed and cut into sections for disposal during an asbestos abatement project. It contained ash like corrosion deposits that smolder after torch cutting. Investigation revealed that burning of carbon and sulfur in the oxygen deficient atmosphere in the ash generated carbonyl sulfide (COS) and carbon disulfide (CS2) gas, which vented when the pipe was moved by the injured construction rigger. This is believed to be the first well documented exposure and response of a human to high concentration COS gas. Sulfur dioxide (SO2) gas is also generated during the cutting. SO2 is almost impossible to inhale and has apparently prevented a similar injury during the cutting. SO2 is almost impossible to inhale and has apparently prevented a similar injury during the many years of US and Canadian heavy water plant de-construction experience. Immediate water quench of the smoldering ash after each cut has eliminated the hazard of residual COS and CS2 gas. This previously unrecognized industrial hazard may be encountered by other chemical and petroleum industries during torch cutting of pipes that contain similar deposits of iron oxide, iron sulfate, sulfur and carbon