ESD Valves manufactures air shutoff valves for diesel engines. Globally, it has been verified that diesel engines can ingest external hydrocarbons and cause a condition called overspeed, which can lead to a catastrophic explosion similar to the BP Texas City Refinery in 2005 or the BP Horizon offshore well in 2010. There are many types of diesel engines and many types of valves used to shut off the air to the intake manifold. ESD Valves makes butterfly designs that are typically less expensive but just as functional and durable as higher end models. Check out the website for more details: www.esdvalves.com