Is DEF Fluid Flammable? Exploring the Flammability of Diesel Exhaust Fluid

If you’ve ever driven a vehicle with a diesel engine, you may have come across the term DEF fluid. DEF, or Diesel Exhaust Fluid, is widely used in modern diesel engines to help reduce emissions and comply with strict environmental regulations. But a common question many people have is, “Is DEF fluid flammable?” In this article, we will answer that question and provide you with all the necessary information about DEF fluid.

What is DEF Fluid?

DEF fluid is a mixture of urea and deionized water. It is a clear, colorless solution that is non-toxic and safe to handle. DEF is not a fuel additive; instead, it is injected into the vehicle’s exhaust stream to break down harmful nitrogen oxides (NOx) into harmless nitrogen and water.

Is DEF Fluid Flammable? Exploring the Flammability of Diesel Exhaust Fluid


Is DEF Fluid Flammable?

No, DEF fluid is not flammable. DEF has a high water content, and water is not a flammable substance. Additionally, DEF is formulated with a high concentration of urea, a compound that is non-flammable. Therefore, there is no risk of DEF catching fire or igniting under normal circumstances.

It is important to note that DEF should always be handled and stored properly to maintain its effectiveness. DEF fluid freezes at around 12°F (-11°C) and can degrade if exposed to direct sunlight or extreme temperatures. However, its non-flammable nature remains unchanged in any condition.

Is DEF Fluid Flammable? Exploring the Flammability of Diesel Exhaust Fluid


Handling and Storage Guidelines

To ensure the integrity and quality of DEF fluid, here are some handling and storage guidelines:

  • Store DEF fluid in a cool, dry place away from direct sunlight to prevent degradation.
  • Do not mix DEF with any other substances, such as gasoline or motor oil.
  • Use only approved containers and dispensing equipment that are suitable for DEF.
  • Do not reuse containers that previously held other chemicals or fluids.
  • Avoid spilling DEF fluid, as it may cause slippery surfaces.
  • In winter, protect DEF from freezing by storing it indoors or using heated storage tanks.

Benefits of DEF Fluid

While the primary purpose of DEF fluid is to reduce emissions, there are several benefits associated with its use:

  • Improved air quality: DEF fluid helps reduce harmful emissions, such as nitrogen oxides, which contribute to air pollution and smog.
  • Compliance with regulations: Many countries, including the United States and European Union, have strict emission regulations that diesel engines must meet. Using DEF fluid helps vehicles meet these requirements and avoid penalties.
  • Engine performance: By optimizing the combustion process, DEF fluid can improve fuel efficiency and overall engine performance.
  • Longer engine life: Reduced emissions mean less stress on the engine components, resulting in potentially longer engine life.

Frequently Asked Questions For Is Def Fluid Flammable? Exploring The Flammability Of Diesel Exhaust Fluid

Is Def Fluid Flammable?

DEF (Diesel Exhaust Fluid) is non-flammable and non-explosive, making it safe for use in various diesel vehicles.

What Is Def Made Of?

DEF is made up of a mixture of urea and deionized water, which helps in reducing harmful emissions from diesel engines.

Can Def Cause Any Damage To My Vehicle?

When used correctly, DEF does not cause any damage to your vehicle. However, it should be stored properly to prevent contamination.

How Should Def Be Stored?

DEF should be stored in a cool, dry place away from direct sunlight. It should also be kept in a sealed container to maintain its quality.


DEF fluid is an essential component in modern diesel engines, enabling them to meet strict emission regulations and reduce environmental impact. It is important to understand that DEF fluid is not flammable and poses no fire risk. By handling and storing DEF properly, you can ensure its effectiveness and contribute to a cleaner and more sustainable future.

Updated: January 25, 2024 — 2:40 am