Is Diesel Fuel Flammable?

Diesel fuel is very easy to find across the United States. 

It is what feeds our cars and vehicles so we can move around freely and go wherever we need to. It is such a useful and vital liquid to our modern society that it is available at every gas station in the country. But what is diesel fuel exactly, and how safe is it for us to use?

Diesel Fuel Is It Flammable

What Is Diesel Fuel?

Diesel fuel is any liquid fuel specifically designed for use in diesel engines, which use compression ignition to light the fuel and power the engine. It comes in three main forms: petroleum diesel, synthetic diesel, and biodiesel.

Diesel fuel is thicker than gasoline so it evaporates slower and has a higher energy density. 

Petroleum diesel is the most common type of diesel fuel. Like gasoline, it starts off as crude oil mined from the earth and is then refined into petroleum diesel.

Synthetic diesel is produced from carbon-containing material like coal or biomass, and biodiesel is obtained from vegetable oil or animal fat. Despite their differences in origin, all diesel fuels have the same kind of properties to be able to work in a diesel engine. 

Is Diesel Fuel Flammable?

According to the US Department of Labor, diesel is classed as a flammable liquid. 

This is because a flammable liquid must have a flashpoint below 140 degrees Fahrenheit. Flashpoint refers to the lowest temperature a liquid will produce sufficient vapr to produce a flammable mixture.

The lower the flashpoint, the more likely a liquid will catch fire in ambient temperatures. The higher the flashpoint, the easier it is to handle the liquid. 

Common diesel fuel has a flashpoint temperature between 125 and 180 degrees Fahrenheit, classing it as a flammable liquid (the change in a flashpoint is relevant to the pressure in the air). 

However, despite the fact that diesel fuel is classed as a flammable liquid, it is not nearly as flammable as other types of fuel. 

For instance, take gasoline. Gasoline has a flashpoint temperature of -40 degrees Fahrenheit. This means that gasoline is extremely flammable.

Even in freezing temperatures, it gives off enough vapor to form a burnable mixture. This makes gasoline a very flammable liquid that can catch fire incredibly easily, making it difficult to handle and transfer safely.

On the other hand, diesel does not have this problem as it has a much higher flashpoint temperature despite also being classed as a flammable liquid. 

If you were to touch gasoline with a burning match - it would ignite instantly and burn until all the fuel is gone. This is why they say never light a match or a cigarette at a gas station, you could cause an explosion by igniting the burnable mixture in the air given off from any gasoline. 

But if you were to touch diesel fuel with a burning match, it would take some time before the gasoline ignited. This is because the diesel fuel needs to be heated up first before it can ignite and catch fire.

In a diesel engine, pressure is used to cause ignition rather than using some kind of energy or flame. This is why diesel engines do not have spark plugs, but engines that use gasoline as a fuel do - they need the spark plug to ignite the air fuel mixture caused by gasoline. 

So even though diesel fuel is classed as a flammable liquid and will catch fire eventually, it is still one of the safer types of fuel to use as it has to be heated to at least 125 degrees Fahrenheit before it can ignite.

Vapors given off by diesel can ignite and explode when mixed with air but as long as diesel fuel is handled with care, this is very unlikely to happen.

Is Diesel Fuel Combustible?

For a liquid to be considered combustible, it needs to have a flashpoint between 100 degrees Fahrenheit and below 200 degrees Fahrenheit. A combustible material will do the same thing as a flammable liquid, only the classification flashpoint temperatures are set at different points. 

As diesel fuel has a flashpoint temperature between 125 and 180 degrees Fahrenheit, diesel fuel is considered a combustible liquid as well as a flammable one. 

What To Do When Diesel Fuel Catches Fire

The first thing you should do if anything ever catches fire, is to call your fire department. Firefighters are trained professionals when it comes to tackling fires and will have the knowledge and equipment necessary to extinguish them.

If you try to put a fire out yourself, you are only risking more danger to yourself. If you ever see a fire, evacuate the area and call 911.

However, if you are expected to put out a diesel fire by yourself, then here is what to do. 

Fires including flammable liquids like diesel are considered Class B fires. In the fire triangle, the diesel is the fuel source for the fire and once the fuel source is used up, the fire extinguishes itself. 

If a diesel fire is starting to get out of hand and poses a serious risk and danger to life and property, then use a Class B Fire Extinguisher. Do not try to extinguish the fire using water - this will only spread the fuel and create even more fire.

Class B fires are extinguished by cutting off the oxygen, so you need to use a carbon dioxide fire extinguisher to suffocate the fire.

You can try to smother the fire using bicarbonate (baking soda) or potassium carbonate, but a trusty fire extinguisher is the best tool to use to stop a fire from spreading. 

To avoid diesel fires in the future, make sure you store your diesel away from sources of ignition and heat. Do not keep any near any open flames and out of strong sunlight.

You should follow this practice with all the flammable and combustible liquids you own in your home, as it greatly reduces the chance of a fire breaking out. If you keep the fuel source away from the ignition source, then a fire cannot start. 

Now, all of your questions about diesel fuel and fire are answered. While diesel is considered flammable and combustible, it needs to be heated before it can ignite, making it a safer fuel to handle and use.

If a diesel fuel has broken out, call 911 and ask for your local fire department or extinguish the blaze yourself using a Class B carbon dioxide fire extinguisher.