Electric forklifts have historically been used in military applications such as unloading ammunition from storage areas due to a regulation which prohibited use of gasoline, diesel, or liquid propane gas (LPG) powered engines. This regulation has been changed to allow diesel powered forklifts if inside ambient air quality remains within safe levels. Diesel powered trucks are preferred over electric power for many military applications due to operational and support advantages. A new requirement for exhaust emissions from diesel powered forklift trucks has been developed by the Army for use in procurement of warehouse diesel trucks in the 4000–6000 lb capacity size. Future procurement by the Army of warehouse diesel forklifts in the 4000 - 6000 lb size will require that engines meet the new requirement for hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOX), smoke and particulates.