Material that in itself is normally stable, even under fire exposure conditions, and is not reactive with water.
Material that in itself is normally stable, but which can become unstable at elevated temperatures and pressures.
Material that readily undergoes violent chemical change at elevated temperatures and pressures or which reacts violently with water or which may form explosive mixtures with water.
Material that in itself is capable of detonation or explosive decomposition or reaction but requires a strong initiating source or which must be heated under confinement before initiation or which reacts explosively with water.
Material that in itself is readily capable of detonation or of explosive decomposition or reaction at normal temperatures and pressures.