Diesel Exhaust Fluid

What is Diesel Exhaust Fluid?


DEF is a 32.5 % solution of high-purity, synthetically manufactured urea in de-mineralized water. It is a safe-to-use fluid. Diesel Exhaust Fluid (DEF) is used in diesel engines with SCR systems to reduce emissions. As the world's largest DEF producer, Yara offers the security of supply and reliable quality DEF.

All diesel commercial vehicle equipped with SCR (Selective Catalytic Reduction) technology, since January 1st, 2010, comply with the emission standards imposed by the EPA Clean Air Act in North America. 

Yara's DEF product is certified according to ISO 22241 (ISO-22241-1, ISO-22241-2, ISO-22241-3). This international standard protects your vehicle from contamination which could cause serious damage. Using a urea solution of incorrect or low quality that does not follow these standards risks costly repairs.

Air1 is Yara’s brand of Diesel Exhaust Fluid. It is supplied via the Mansfield DeliveryONE Network of distributors across the US, so you are never far away from an Air1 North American distributor.

Ed Wells
Ed Wells
VP, Environmental Solutions, North America
Practical tips
Practical tips

Practical tips

DEF is very easy to use and is a harmless substance. It is not a fuel, nor a fuel additive but a high purity urea solution that must be used in a dedicated tank on your vehicle, that should just be refilled as and when required. DEF is non-flammable and non-explosive. It is classified as a transportable fluid with minimal risk. If you ever spill DEF on your hands, simply wash them thoroughly with water. Learn more about how to use DEF:

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Where can I order DEF?

Diesel Exhaust Fluid from Air1 is available at forecourts of fuel retail stations, retail outlets and at official Air1 distributors who also supply fuel, oil and other spare parts for commercial diesel vehicles. These distributors belong to Mansfield DeliveryOne Network and are located nationwide, across the USA.

To find your nearest Diesel Exhaust Fluid supplier stocking Air1, click here: Where's my nearest Diesel Exhaust Fluid Supplier?

To find your nearest Diesel Exhaust Fluid Retail Outlet selling Air1, or one that is on your delivery route, click here: Where's my nearest Diesel Exhaust Fluid pump?

You can also download our free App showing where Air1’s nearest Diesel Exhaust Fluid pump is to your current location, or on the route you will be taking.

Download the Diesel Exhaust Fluid app for Android

Download the Diesel Exhaust Fluid app for iOS

How is Diesel Exhaust Fluid used?

The driver/operator of the vehicle fills Diesel Exhaust Fluid into a dedicated Diesel Exhaust Fluid tank (which is separate to the diesel tank) located on the vehicle chassis. There is usually a blue filler cap/lid which states "Diesel Exhaust Fluid" on the top. Diesel Exhaust Fluid is automatically injected into the tail pipe of the vehicle from the Diesel Exhaust Fluid tank by the SCR technology.This is before the SCR catalyst, but after the engine.

As the Diesel Exhaust Fluid heats up in the exhaust gases, it converts into CO2 and ammonia. Once inside the SCR catalyst, the nitrogen oxide (NOx) gases from the exhaust pipe, react with the ammonia. This changes the harmful NOx gases in the exhaust to nitrogen and steam which is released to the atmosphere. Nitrogen is an already occurring harmless atmosphere gas.

Diesel Exhaust Fluid is usually replenished during your service or sometimes your Diesel Exhaust Fluid warning light will indicate that you need to refill beforehand. Running dry of Diesel Exhaust Fluid may cause your vehicle to operate in crawler mode (go slow). Refilling is easy, use clean Diesel Exhaust Fluid apparatus (ie don't use oil or diesel funnels), take off the filler cap, pour until full. For smaller vehicles the tank cap is usually in the boot, under the carpet. Wipe up any spills as it can corrode some metals/paintwork.

Diesel Exhaust Fluid is ideally purchased from your Car/RV/Pickup truck dealership. However, it is also available at Truck stops, truck dealerships and Oil distributors who supply the truck industry. They may have Diesel Exhaust Fluid containers or pumps that passenger vehicles can use, but please investigate on arrival.

How does Diesel Exhaust Fluid work with SCR?

Diesel Exhaust Fluid, is a synthetically made urea solution which has to be API certified and meet an ISO standard. Diesel Exhaust Fluid is a safe to use fluid which is filled into a separate tank on the vehicle. It is then injected into the exhaust pipe, in front of the SCR catalyst, downstream of the engine. Heated in the exhaust it decomposes into ammonia and CO. When the NOx from the engine exhaust react inside the catalyst with the ammonia, the harmful NOx molecules in the exhaust are converted to harmless nitrogen and water, which are released from the tail pipe as steam.

View our Quick Guide to SCR and Diesel Exhaust Fluid (5 slide presentation).

Learn more about DEF