text: Phosphine is an attractive fumigant because it is lethal to insects and rodents, but degrades to phosphoric acid, which is non-toxic.  As sources of phosphine, for farm use, pellets of aluminium phosphide (AlP), calcium phosphide (), or zinc phosphide () are used.  These phosphides release phosphine upon contact with atmospheric water or rodents' stomach acid. These pellets also contain reagents to reduce the potential for ignition or explosion of the released phosphine. 
  An alternative is the use of phosphine gas itself which requires dilution with either  or  or even air to bring it below the flammability point. Use of the gas avoids the issues related with the solid residues left by metal phosphide and results in faster, more efficient control of the target pests. 
  One problem with phosphine fumigants is the increased resistance by insects.