Phosphine

Very dangerous fire hazard by spontaneous chemical reaction.

Moderately explosive when exposed to flame.

Pure phosphine does not spontaneously ignite in air below 150 deg C unless it is thoroughly dried, when it ignites in cold air. The presence of traces (0.2%) of diphosphane in phosphine as normally prepared causes it to ignite spontaneously in air, even at below -15 deg C ... Traces of oxidants promote pyrophoricity.

Spontaneously flammable in air if there is trace of /diphosphane/ present; burns with luminous flame.

Flammable gas. Pyrophoric; may ignite spontaneously in air or accumulate and explode in air without source of ignition.