DEF is a non-hazardous, non-toxic, non-flammable material that lowers NOx concentrations. DEF does not pose any serious health risks to people, so it is safe to handle.  Photo courtesy of Peak C&I

DEF is a non-hazardous, non-toxic, non-flammable material that lowers NOx concentrations. DEF does not pose any serious health risks to people, so it is safe to handle. Photo courtesy of Peak C&I

Today’s modern diesel engines need Diesel Exhaust Fluid to help them stay in compliance with federally mandated diesel emissions standards to reduce NOx emissions.

DEF is a mix of deionized water and high-purity urea (automotive grade aqueous grade) in a 67.5% to 32.5% blend. It is a non-toxic fluid that is injected into the diesel engine’s exhaust stream. When heated, DEF divides into ammonia and carbon dioxide. The water in the DEF vaporizes as it enters the exhaust stream and the ammonia molecules move to the catalytic converter where their job is to neutralize NOx turning it into harmless nitrogen and water.

It’s important to monitor the amount of DEF in the tank because if the fluid runs out the vehicle will lose power and its speed will be severely limited, forcing the driver to limp home. Onboard warning systems alert drivers when DEF is running low and needs to be replenished.

One common concern about DEF is that it can freeze. Once its temperature reaches 12°F it will freeze but there is no cause for concern. The vehicle will still be able to start and operate normally. As the engine warms up the DEF will thaw. Be aware that DEF expands about 7% when frozen and DEF tanks are built to accommodate that expansion. Caution your drivers not to overfill the DEF tank, especially when operating in cold weather.

DEF purity is very important as is the proper urea-to-water ratio, so make sure you purchase DEF from a reputable supplier. One way to ensure you are getting high quality DEF is to look for the American Petroleum Institutes symbol on the container.

It is also important that DEF be kept pure so proper storage and handling are extremely important in order to avoid contamination. (See A Guide To DEF Storage & Contamination for more specifics on the proper handling and storage of DEF.)

DEF comes in a variety of sizes including 1-gallon containers, 2.5- gallon containers, 55-gallon drums and 275-gallon totes. DEF is also available at truck stops and diesel engine repair facilities.

Originally posted on Work Truck Online