Modified Tobacco Warehouse Aerations For Lowered Acute Emissions of Phosphine Into Surrounding Environs

Abstract

Regulations of atmospheric emissions of phosphine have been enacted by a number of states in the U.S. The maximum concentration allowed at the property of fumigated sites addresses not environmental contamination, but rather the health and safety of citizens in the proximity of warehouse fumigations. In a warehouse fumigation, phosphine is most rapidly vented just after opening the warehouse for aeration. Therefore, alternative aeration techniques were tested with the objective of minimizing peak concentrations outside the warehouse through a slower and more uniform emission rate. Three types of warehouse aerations were tested: (1) a standard aeration with all doors and vents open for 3 d, (2) a modified aeration with only roof vents open for 1 d and then all doors and vents open for the following 2 d, and (3) a second modified aeration with only one large door open for 1 d and then all doors and vents open for the following 2 d. Rates of phosphine emission from the warehouses throughout aeration, gas concentrations downwind from the warehouse, and the adequacy of aeration in both the commodity and warehouse freespace were determined. Modified aerations greatly reduced phosphine peak emission rates, adequately aerated the warehouse freespace, and for most application situations, adequately aerated the tobacco. At one warehouse complex, the three types of aeration (Standard, Roof-Vent-Only and Door-Only) released 45.7, 8.5 and 9.7%, respectively, of the available gas during the first 30 min of aeration. Compared with the Standard aeration, both types of modified aeration delayed aeration of both freespace and tobacco by less than 24 h. Outside downwind concentrations of phosphine were greatly reduced by the modified aerations, especially the Roof-Vent-Only in which downwind concentrations were virtually undetectable.