DEF Glossary

Diesel exhaust fluid commonly referred to as DEF, is relatively easy to use on a practical level. However, there are many aspects of its creation and handling that are quite complex. To help interested parties understand the full scope of DEF and its industry impact, Blue Network has collected a glossary of important terms.

Agencies and Organizations

Due to its nature, DEF must be handled with extreme care. To ensure this, professional organizations set standards. Government agencies overseeing environmental protection may also influence the use of DEF.

Equipment and Technology

DEF is a fragile substance that needs to be handled by special equipment to be transported and stored.


Also called Intermediate Bulk Containers, or IBCs for short, totes are containers used in the distribution and storage of DEF. They can carry 1041 to 1249 litres and are the standard for liquid chemical transport.

Particulate Matter

Pollutants comprised of solid particles such as unburnt fuel are called particulate matter. Particle size can vary; particles measuring less than ten μm are considered “small.” While both large and small particles are dangerous, those considered small are even more so. This is due to the damage they can do to the lungs.

Selective Catalytic Reduction (SCR)

SCR describes emissions after-treatment technology. It introduces an oxidation catalyst and urea into the exhaust stream to instigate a chemical reaction that turns NOx into water and nitrogen. In addition to protecting public health, this technology aims to improve fuel efficiency.

On-Board Diagnostics

This electronic telemetry system keeps drivers in the loop by reporting operating parameters. Built into vehicles, it monitors the emissions control system and applies torque penalties if said vehicles don’t have DEF.

Nitrogen Oxides (NOx)

NOx is a scientific term that refers to a variety of nitrogen oxides. These are chemical compounds comprised of nitrogen and oxygen atoms. While there are many, the two most concerning are nitrogen dioxide (NO2) and nitric oxide (NO). When they combine with naturally occurring chemicals in the atmosphere, they can create smog or acid rain.

ISO 22241

ISO 22241 describes the international quality standard for DEF distribution, production, and storage. There are five parts:


  • Handling guidelines
  • Materials
  • Quality
  • Contamination
  • Urea concentration


The full guidelines are published by the International Organization for Standardization.

Exhaust Gas Recirculation (EGR)

This technology cools exhaust and returns it to the engine inlet. As a result, the combustion temperature lowers, and there are fewer emissions.