DOW CHEMICAL-EXPOSURE INDEX GUIDE

A number of events in the 1970's and 1980's impacted the course of pro cess safety. Incidents such as Flixborough, Seveso, Three-Mile Island, and Bhopal are well known throughout industry and are recognized as e xamples of major disasters. Even though events leading up to these dis asters were completely different they had one common element between t hem: a substance was released from a manufacturing unit, became airbor ne and presented a hazard of such magnitude as to place the safety of both employees and the surrounding public in jeopardy. As a result, in dustry became increasingly concerned regarding potential loss, in huma n and economic terms, as plants and equipment grew in size [1]. The Fl ixborough incident raised the level of concern for process safety, par ticularly in terms of the hazards presented by fire and explosion. Sev eso and Three-Mile Island emphasized the need to consider far-field ex posure. The Bhopal incident created an urgent need to recognize and un derstand the expected downwind impact of potential releases of acutely toxic substances to the air. In order to meet this need, the Dow Chem ical Company, a recognized leader in the area of safety and loss preve ntion, presented a Chemical Exposure Index in 1986. AlChE has recently published an updated version entitled Dow's Chemical Exposure Index G uide (first edition).