Phosphine fumigations of wheat in 2500 m 3 steel bins without recirculation facilities

Abstract

Experiments were conducted to assess the effectiveness of introducing aluminium phosphide formulations to generate phosphine gas (PH 3) at the top of a grain bin. It was found that when phosphine-generating formulations (blankets) are placed in the headspace between the grain surface and roof of a grain bin, the fumigant is distributed by convection currents. A suitably gas-tight bin of 2500 m 3 ( c. 2000 t) can be fumigated effectively within 20 days, in all seasons, by application of 0.5 g m −3 of phosphine generated by one blanket (Detia ® and Celphos ® blankets proved equally effective). Ductwork is essential to facilitate fan-forced and natural ventilation after fumigation is completed. Ventilation to satisfy current standards for fumigation clearance can be achieved in five days, but phosphine concentrations in the headspace must be checked before grain is transported, as sometimes additional ventilation is necessary. Blankets containing the spent phosphine-generating formulation were readily removed from the grain surface at the completion of the fumigation.