Diesel Exhaust Fluid Frequently Asked Questions

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Why do I have to use an SCR system and DEF?

As part of the Clean Air Act of 1970, the Environmental Protection Agency (EPA) has mandated that all on-road diesel vehicles manufactured January 1, 2010 or later must be equipped with technology to reduce NOx emissions. All diesel vehicles from class 1 to class 8 are included in this requirement.

What is DEF?

Diesel Exhaust Fluid is one of the key participants in the Selective Catalytic Reduction (SCR) process. It is a non-toxic, colourless and odourless solution of 67.5% of pure de-ionized water and 32.5% DEF grade urea that meets ISO 22241 specifications. DEF converts Nitrogen Oxide (NOx) into nitrogen gas and water vapour. It is a stable and non-flammable liquid.

What is Urea?

Urea is a nitrogen compound that turns to ammonia when heated. It is used in a variety of industries, including fertilizer in agriculture. Urea occurs naturally but is also commonly made from natural gas.

What is Selective Catalytic Reduction?

The process starts with low sulphur diesel fuel combusted in a diesel engine where hot diesel exhaust gases flow through a filter towards a SCR catalytic converter. DEF from an onboard storage tank is injected into the exhaust stream right before the catalytic converter. In the catalytic converter DEF reacts with NOx to convert it into harmless nitrogen and water vapour. Testing has shown that SCR systems may result in a 4-6% fuel savings over standard engines.

What is the shelf life for DEF?

DEF should be kept in a clean environment and handled carefully to prevent contamination which could lead to damage of catalytic converters. In order to maintain DEF product integrity, the SCR industry has adopted strict standards for DEF manufacturing, blending, storage, dispensing and testing. These standards are ISO 22241-1, ISO 22241-2, and ISO 22241-3. The DEF solution is temperature sensitive, therefore when stored in extreme temperature environments, DEF must be housed in a climate controlled building. Storage temperature greater than 25ºC should be avoided. Under 25ºC minimum shelf life is 18 months.

How should DEF be stored and dispensed?

DEF can only be stored in stainless steel, coated carbon steel, or in a specific high density plastic container. Materials specifically not recommended include non-ferrous metals and alloys (copper, aluminium, magnesium, silver, zinc, lead), solders containing non-ferrous metals, and nickel-coated plastics and metals. Clean dispensing equipment made with DEF compatible materials must be used with AirDEFender.

What happens if DEF freezes?

DEF will freeze at -11ºC. The engine will still start and run if the DEF is frozen since a DEF tank heater will ensure that it thaws quickly. DEF is not compromised when frozen and thawed. DEF will expand about 7% when frozen but there is space in the tank for that.

Is DEF hazardous?

airDEFENDER is a WHMIS controlled substance, considered to be an irritant to the eyes and skin. It is a stable and non-flammable, non-explosive solution. When used under normal conditions, it is not expected that there would be any significant health hazards. Should it come into contact with your skin, eyes or even your vehicle, you should still rinse thoroughly with water. Wearing clean gloves when dispensing should ensure that the DEF will not get contaminated. DEF is corrosive to some metals, so anything it spills on should always be rinsed off with water.

What happens if the vehicle runs out of DEF?

Vehicles are equipped with a DEF gauge on the dash to alert the driver on the fluid level. If the level becomes low an alert will let the driver know the DEF tank needs filling. If the driver runs out completely the vehicle power will be reduced to encourage the operator to refuel the DEF tank. Once the DEF tank is refuelled, normal power levels will be restored on the vehicle.