Phosphine, (PH3)

A highly toxic, flammable gas that is odorless in its purest form, although the usual presence of substituted phosphine and diphosphane give it a highly unpleasant odor, while the presence of diphosphane may make it spontaneously flammable in air in sufficient quantities. Phosphine is used in pest control, especially in transportation, where it is the only fumigant that is allowed, cost-effective, rapidly acting and does not leave residues in the stored product. Phosphine is detectable with colorimetric gas sampling tubes, while many manufacturers carry electrochemical phosphine sensors.