BD Diesel Positive Air Shutdown - Chevy 2004.5-2010 LLY/LBZ/LMMWhen you need an emergency engine shutdown system, then BD has the solution that is hard to PASs up. Some industries such as mining, oil refinery, forestry, mobile welding, septic removal and refueling require some vehicles to have an emergency engine shutdown in place. The most effective method for this is to cut the air supply to the Diesel engine ensuring fuel ignition to cease. With BDs Positive Air Shutdown (PAS), an inline butterfly valve is