Substance hazard index (SHI)
The substance hazard index (SHI) is an index developed to identify objectively the toxic chemicals or substances that could be involved in a catastrophic release. The index is a simple function of vapor pressure and toxicity: the higher a substance’s vapor pressure, the more readily it will enter the atmosphere in the event of a release. The greater a substance’s toxicity, the lower the concentration required to present a hazard, and the higher its SHI. A more detailed definition, along with an illustrative list of substances and their SHIs, is presented in Appendix C.
Source: API RP 750, Management of Process Hazards, First Edition, January 1990. Global Standards