DEF is an aqueous urea solution comprised of 67.5% deionized water and 32.5% high-purity urea. This mixture does not support combustion or have a flash point that would make it explosive.
The lowest temperature at which a liquid can evaporate and combine with air to generate an ignitable combination is known as the flash point. Something needs to have a flash point of less than 100°F (37.8°C) in order to be flammable. DEF cannot catch fire or explode because it lacks a quantifiable flash point.
Is diesel exhaust fluid flammable? DEF manufacturers and industry groups emphasize that DEF is non-flammable and non-combustible. It will not ignite or burn. DEF containers even have warning labels stating that the solution is non-flammable.
Proper handling and storage of DEF are still important. Any solution comprised of chemicals can become hazardous depending on how it is used. Follow guidelines on using appropriate containers, avoiding excess heat or cold, and preventing Contamination. But rest assured that DEF is designed to be an inherently stable, non-flammable formula. Let’s learn more in this article by Azure Chemical.
Contents
Chemical Composition
Diesel exhaust fluid (DEF) primarily comprises urea and deionized water. Urea, which makes up around 67.5% of DEF, is a carbon, nitrogen, oxygen and hydrogen compound. It helps to convert the NOx emissions from diesel engines into nitrogen gas and water vapor.
The deionized water in DEF, making up approximately 32.5% of the fluid, dissolves the urea and allows it to be sprayed into the exhaust stream. Deionized water has had ions like calcium and chlorine removed to increase purity.
DEF also contains small amounts of additives and stabilizers. These help to prevent the growth of bacteria and algae in the DEF, ensure proper freezing and thawing, and prevent DEF from degrading over time. Common additives include inorganic salts, ammonia, and amine compounds.
The precise ratios and components in DEF can vary slightly between manufacturers. But urea and deionized water remain the two primary constituents.
How DEF works
Diesel exhaust fluid (DEF) works by chemically reducing the oxides of nitrogen (NOx) emitted by diesel engines into nitrogen and water vapor.
Between the diesel particle filter and the selective catalytic reduction (SCR) catalyst, DEF is injected into the heated exhaust gasses.
The DEF sprayed into the exhaust reacts with the SCR catalyst to trigger chemical reactions that convert the NOx into harmless nitrogen gas (N2) and water vapor (H2O). Specifically, the DEF breaks down into ammonia (NH3), which reacts with the NOx on the SCR catalyst surface to reduce the NOx into N2 and H2O.
By converting the harmful NOx emissions into inert nitrogen gas and water vapor, DEF dramatically reduces the NOx pollution from diesel vehicles and equipment. Most modern diesel engines are designed to run with DEF, allowing them to meet even the most stringent emissions standards.
Proper Handling and Storage of Diesel Exhaust Fluid
Diesel exhaust fluid (DEF) must be properly handled and stored to maintain quality and effectiveness. Here are some key considerations:
Avoid Extreme Temperatures
DEF freezes at about -11°C, or 12°F. DEF can deteriorate more quickly in high temperatures above 86°F (30°C), so keep it in a cool, dry place with a temperature between 23 and 77°F (-5 and 25°C).
Prevent Contamination
Keep the DEF storage tank and dispensing systems clean. Even small amounts of Contamination from dirt, water, engine coolant, or other chemicals can degrade DEF quality. Use dedicated DEF containers, funnels, etc.
Check for Signs of Contamination
Look for unusual coloring, odor, viscosity, cloudiness, or sediment, which may indicate contaminated DEF fluid. Test the urea concentration if Contamination is suspected.
Avoid Direct Sunlight
Sunlight exposure over long periods can accelerate the degradation of DEF. Store containers out of direct sunlight.
Seal Containers Tightly
Leave no headspace in partially used containers, and keep caps tightly sealed to avoid evaporation or spillage of the DEF.
Store DEF Safely
Avoid heat, sparks, open flames, strong oxidizers, and other ignition sources since DEF can combust under certain conditions despite not being directly flammable.
Proper handling and storage practices will help maintain optimum DEF quality and performance over time. Check your owner’s manual for additional DEF storage instructions for your vehicle.
Dangers and Risks
While diesel exhaust fluid is generally considered safe when handled properly, there are some risks and dangers to be aware of.
Skin and Eye Irritation
Diesel exhaust fluid can cause mild skin irritation with prolonged exposure due to its slightly alkaline chemical properties. The most common symptoms are redness, itching, and burning or stinging sensations on exposed skin. DEF is not likely to cause serious burns, but sensitive skin may react more strongly.
DEF can also irritate the eyes if splashed or sprayed directly, causing redness, watering, and stinging. Proper eye protection, like safety glasses, is recommended when working with DEF to prevent eye exposure. Immediately rinse eyes with cool water if DEF makes contact.
Ingestion
Swallowing diesel exhaust fluid is harmful and requires immediate medical attention. Ingesting large amounts can potentially be life-threatening without swift treatment.
Common symptoms of DEF ingestion include nausea, vomiting, diarrhea, low blood pressure, headache, abdominal pain, respiratory issues, and metabolic disturbances. The alkaline nature of DEF can damage the tissues of the esophagus and stomach. Seek emergency medical assistance right away in case of accidental ingestion.
Fire Hazards
Diesel exhaust fluid can react with other substances and increase the risk of a fire even if it is not combustible. Both OSHA and the NFPA classify DEF as a “combustible liquid”.
Spilled DEF on hot engine components can produce harmful nitrogen oxide fumes and ammonia vapors. Contamination with diesel fuel, hydraulic fluid, or other combustible substances can also increase DEF’s flammability. Proper storage, handling, and refilling procedures should be followed to minimize fire hazards.
DEF Quality Standards
Diesel exhaust fluid (DEF) must meet certain quality standards for optimal performance in reducing NOx emissions.
Guidelines for DEF quality have been set by the American Petroleum Institute and the International Organization for Standardization (ISO):
ISO 22241
This global standard specifies DEF’s required properties and test methods. It sets limits for DEF concentration, alkalinity, impurities, density, freezing point, and other parameters. ISO 22241 aims to ensure the DEF is pure and stable.
API Guidelines
The API’s guidelines complement ISO 22241 with additional DEF testing procedures and storage requirements. They help maintain DEF quality throughout transportation, handling, and storage.
By mandating DEF testing and certification, these standards verify that the DEF sold at refueling stations and in containers meets composition and purity requirements. Contaminated or degraded DEF can corrode SCR systems and reduce NOx conversion, so compliance with ISO 22241 and API guidelines is critical.
Fleet operators should only use DEF that meets the standards. Containers and dispensers should be properly labeled to indicate certification. Additionally, operators must follow DEF storage and handling best practices to avoid Contamination after purchase. Proper handling keeps the DEF within the purity specifications required for effective NOx reduction.
Refilling DEF
Refilling your vehicle’s diesel exhaust fluid (DEF) tank requires using the correct nozzles, tanks, and gauges to avoid Contamination.
Here are some tips:
Use the Right Nozzles
– Only use DEF-designated filling equipment and nozzles. Regular diesel/gas nozzles can contaminate the DEF tank.
– Look for blue filler caps and necks on DEF tanks to prevent accidental misfueling.
– Never put any other fluid besides DEF into the DEF tank.
Check the Tank Level
– Check the DEF gauge on your dashboard to see current tank levels.
– Wait until the tank level drops below 1/4 full before refilling. Filling too early can lead to spills.
– Refer to your owner’s manual for specifics on the DEF tank level and refill procedure.
Prevent Contamination
– Wipe any DEF spills or residue from the nozzle/tank opening before refilling to avoid Contamination.
– Avoid letting dirt, dust, or water enter the tank during filling.
– Never top off the tank after the automatic shutoff nozzle clicks. This can lead to spills.
Following the proper DEF refilling steps will keep your diesel exhaust fluid pure and your vehicle’s emissions system running smoothly. Let the tank get low, use the right nozzle, and prevent Contamination.
DEF Shelf Life
Diesel exhaust fluid (DEF) does degrade slowly over time.
The shelf life for DEF is typically 12-18 months from the manufacturing date with proper storage.
The key factors that affect DEF’s shelf life and quality are exposure to heat and Contamination. To avoid contamination, DEF should be stored in a cool, dry place from 12°F to 86°F and kept sealed in its original container.
DEF deteriorates more quickly in hot temperatures exceeding 86°F over an extended period of time. The efficiency of the DEF is decreased as the urea concentration starts to drop.
To maintain optimal quality, DEF recommends a usage cycle of 12 months from the manufacture date. Most DEF containers have an expiration or best-by date stamped on them, indicating the end of the suggested shelf life.
However, degraded DEF may still be usable past its expiration date, although the efficiency may decrease over time. Always check the DEF quality if it is older than 12 months.
Properly stored DEF has a long enough shelf life for consumer vehicle usage. But fleets with large DEF supplies should follow first-in, first-out usage and replace any batches over 12 months old.
Following the manufacturer guidelines for storage and avoiding Contamination optimizes the shelf life of diesel exhaust fluid.
Frequently Asked Questions
Is Diesel Exhaust Fluid Flammable?
No, DEF is not flammable. It is a water-based solution and does not pose a fire hazard.
At What Temperature Does DEF Freeze?
DEF begins to freeze at approximately -11°C (12°F). However, freezing does not affect its quality, and upon thawing, it can be used without any issue.
Can DEF Cause Combustion If It Contacts Hot Engine Parts?
No, due to its high water content and chemical properties, DEF does not ignite or cause combustion when in contact with hot engine components.
What Are the Storage Recommendations for DEF?
DEF should be stored in a cool, dry, and well-ventilated area. Avoid direct sunlight and extreme temperatures to maintain its efficacy.
Conclusion
Diesel exhaust fluid (DEF) is an important liquid used to lower emissions in diesel engines. While it contains urea and deionized water, DEF itself is not flammable.
However, DEF can decompose into ammonia, which is flammable at high temperatures. Proper handling and storage of DEF is, therefore, essential. Please keep it away from open flames or other ignition sources—store DEF in a cool, well-ventilated area out of direct sunlight.
When refilled correctly and used as intended, DEF is safe for diesel engines and the environment. Check the DEF gauge regularly, refill it promptly when low, and use a reputable brand that meets API or ISO quality standards. With responsible use, DEF helps diesel vehicles meet emissions regulations.
So, is diesel exhaust fluid flammable? The bottom line is that DEF itself is not flammable, but improper use or storage can lead to the formation of flammable ammonia. Follow the manufacturer’s recommendations for using DEF in your vehicle. This ensures you get DEF’s emissions reduction benefits while avoiding any potential hazards. Have more questions about DEF? Don’t hesitate to contact us at Azure Chemical.
