Frequently Asked Questions


SCR is a technology that is being incorporated into existing exhaust systems to help meet 2010 Environmental Protection Agency (EPA) standards for NOx emissions. It works by injecting small quanitites of DEF into the exhaust stream. When the comingled DEF and NOx come into contact with the SCR unit, the NOx is converted into harmless nitrogren and water.

The SCR unit reduces the NOx in the exhaust gas by reacting it with the Diesel Exhaust Fluid (DEF) and a catalyst.


DEF is a nontoxic solution of 67.5% pure water and 32.5% environmental grade urea. It is a stable fluid that is colorless and odorless. DEF has been widely used in Europe for this same purpose.

No. The Enviromental Protection Agency (EPA) classifies DEF as "non-hazardous" and does not require special handling such as fuel, brake fluids or antifreeze do. It is nonpolluting and nonflammable. More specific detail can be found on our SDS sheet.

DEF is corrosive to certain metals such as aluminum, copper and brass. Storage tanks and dispensing equipment should be made of stainless steel or high density polyethlene.

Urea is a material that is primarily ammonia and carbon dioxide. It is used in a variety of industries, most commonly as fertilizer in agriculture. Urea is naturally occuring, but is commonly made from natural gas.

No. The concentration and purity standards required of DEF in order to maintain the performance and life of the SCR catalyst are very strict. It would be difficult for any end user to meet these standards as outlined in the ISO 22241 guidelines.

All North American OEMs have converged around the following specifications for purity and composition as specified in ISO 22241. Another equivalent but less common specification is AUS32.

The American Petroleum Institute has developed a voluntary quality certification program that ensures North American supplies of DEF will meet the standards mentioned above including standards of product manufacturing, handling, quality assurance, safety and environmental protection. They will do this by testing DEF bought in the field for compliance.


DEF should be stored in temperatures between 12 and 80 degrees F and in a dry, well-ventilated area. It should also be stored out of direct sunlight. Exposures to higher temperatures for short periods of time should not impact the quality of the product. See ISO 22241 for more details on storage.

When stored as instructed in ISO Spec 22241, the minimum shelf life is two years. Note that all API Certified material will be date stamped so the age of the DEF is easily obtained. Also, note that even if the DEF is stored at higher temperature, shelf life will exceed one year.

DEF will begin to freeze at 12 degrees F. If this occurs, you can thaw the material without any impact on the quality of the product.

Not at this time. This is due to the fact that all engines were EPA certified using the precise formulation in DEF. By using an additive, you could negatively impact the performance of the SCR unit and invalidate your OEM warranty.

Yes. Long term storage in high temperatures may reduce shelf life to one year. Occasional high temperature storage should not have an impact on the DEF.

No. DEF is a nontoxic material and does not require special handling. It is also nonpolluting, non-hazardous, and nonflammable. More specific detail can be found on the SDS provided.


DEF usage will vary by vehicle. Most OEMs claim usage will equal 3% of diesel fuel consumption.

OEMs are incorporating dashboard indicators for DEF similar to the ones used for fuel. It will include DEF levels in the tank and provide a low level warning. If the DEF tank runs out completely, the vehicle power will be reduced enough to encourage the driver to refill the tank. The vehicle will not be shut down.

OEMs have designed their SCR systems in a way that provides heat to the DEF tank and supply hoses. The vehicle will start and run as normal even if the DEF becomes frozen. The heating system will quickly thaw the DEF and it will operate without issues.

Yes. Make sure that your equipment supplier has certified that their drum and tote dispensers and nozzles are compatible with DEF.