Chemical reactivity is the tendency of a chemical to react with others. Unlike other types of major hazards, chemical reactivity depends not only on the intrinsic properties of the chemicals but also on the conditions under which they are used. Reactivity incidents occur when control is lost of intended chemical reactions or when unintended chemical reactions take place. The majority of chemical reactions liberate energy and many reactivity incidents involve the release of energy in quantities or at rates too high to be absorbed by the immediate environment. The possible consequences of reactivity incidents are more diverse and complex than those for other types of major hazards. Consequences vary according to the type of chemical reactivity hazards present and the circumstances involved.
Significant work has been performed on understanding chemical reactivity hazards but much less attention has been paid to the identification of reactivity hazard scenarios using process hazard analysis (PHA). PHA should be used to identify reactivity hazard scenarios for each operation in a facility where chemical reactivity hazards may be present. PHA teams must be able to recognize the potential for incidents involving chemical reactivity hazards. They should understand how such incidents can be initiated and their consequences, know how they can be recognized and detected, be aware of safeguards for protecting against them, and know what response actions are appropriate.
This article discusses the consideration of chemical reactivity hazards in PHA and explains how reactivity hazard scenarios can be identified in PHA. Pitfalls in performing PHA that address chemical reactivity hazards are also identified.