Is carbon dioxide flammable?

In this article we will discuss the following: “Is carbon dioxide flammable?”. We will also explain what carbon dioxide is and the chemistry involved.

Is carbon dioxide flammable?

No. Carbon dioxide is not flammable, there are no fire hazards related to it and it will not ignite under any circumstance you could provide in your place. Carbon dioxide is the byproduct (the rest) of the combustion reaction.

What is carbon dioxide?

Carbon dioxide is a chemical compound that has the formula CO2.

It is a colorless and tasteless gas. It can be found naturally and as a result of fossil fuel burning, among other many sources of greenhouse gases.

Carbon dioxide is used by plants, algae, and cyanobacteria as food in the photosynthesis process, and is also released by them upon respiration.

As a primary source of carbon, CO2 is necessary for the sustain of life on earth. At the same time, the increase of carbon dioxide in the atmosphere enhances global warming, leads to the extinction of endangered species, and makes food more expensive to us.

Not even the Covid pandemic could slow down the increase of CO2 in the atmosphere.

Since the gas is not much reactive, carbon dioxide is commonly used as propellant gas. It works by dragging other gases through ducts and valves, in our deodorant cans and industries, for example.

Basic Chemistry

To have some more in-depth about carbon dioxide, first, we need to state a few important scientific facts.

Energy and mass

We can separate the things in the universe into two big groups: energy and mass.

For something to exist in our world, scientifically speaking, it must have mass, energy, or both. Otherwise, it is “nothing”, literally.

Some scientists also believe that mass is something like condensed energy, but this requires more investigation.

Energy comes in many forms. Heat is one of them, sunlight, the light from a bulb, and many other forms of radiation.

And mass is anything that has weight, anything we can put in a kitchen scale and weigh out. Of course, there are many things too light to weigh, but you got the idea.


Anything that has mass is made of atoms. There are a few other things smaller than atoms that have mass, but this is not important right now.

Atoms are the smallest unit of ordinary matter. They are the building blocks that compose the mass. You can imagine them like little balls, but a dandelion or a tiny planet is a better explanation.

This is because atoms are made of a nucleus and an electron cloud. The part of the atom that has practically the whole mass is the nucleus (made of neutrons and protons, highly bonded together).

In the dandelion analogy, the electrons would be its seeds. In the ‘tiny planet’ analogy, the atmosphere would be the electrons. Their center would be the nucleus.

I like the dandelion analogy the most because atoms can lose or receive electrons. I like to think about the seeds flying away.

There are a lot of things that we could say about atoms and how they compose our universe, but let’s go straight to the point so the reader doesn’t fall asleep.

Carbon and oxygen are the atoms that we must talk about now.


As you probably know, life on our planet depends on carbon. And is not because life would cease if carbon simply ran away, it is because carbon is life. Is what constructs our bodies.

It’s like trying to explain what a car is without metal.

Carbon can bond with many things, and that’s why its properties are so wide (or vice versa).

Carbon chemistry still hasn’t been fully exposed, and perhaps never will. These tiny particles are capable of composing both our DNA, the structure of a diamond, the fuel in our cars, and the trees by simply making different connections.


Oxygen is also very interesting. 

You probably heard about oxidation. The term oxidation was given after oxygen, due to its importance.

In very simple terms, when we say that something was oxidized (let’s say, a sliced apple that turned brown) it means that oxygen got inside it. Then reacted and became a part of it.

When an apple’s flesh is exposed to oxygen, its naturally available antioxidants (which is a self-explanatory word) will take care of it. It’s a self-defense mechanism.

When an atom loses electrons it becomes positively charged. If loses, it becomes negative. Oxygen dislikes becoming positive and feels really happy by turning negative, due to the loss of electrons.

When oxidation happens, it means that the oxidized entity (an apple, like in our previous example) had lost electrons. Many molecules can receive these electrons, but oxygen is the most common.

The fire

You may think about fire as a force of nature but it is much more simple than that.

Fire is what we see as the result of a combustion reaction. A combustion is just a specific form of oxidation

Not all oxidations are burnings, but all combustions are oxidations.

Fire takes place once oxygen reacts chemically with a source of fuel. Normally, this source is an organic compound. 

The reaction breaks down the fuel molecules. The carbon (C) was bonded with other carbons and hydrogens (H), but it is an opportunist that only cares about its stability, so he abandons hydrogen and marries oxygen forever (or until he finds an even better partner).

In fact, most carbon bonds have two atoms of oxygen (O). This is the carbon dioxide molecule (CO2). Some eventually bond with only one oxygen, and those we name carbon monoxide, but they are not happy.

But hydrogen, which is not dumb, also goes straight to other oxygen molecules. From this bonding, water (H2O) is the result.

This is essentially why carbon dioxide can’t catch fire. No more oxygen can get inside of it, react and bond, because there is already oxygen in there.

Carbon dioxide


This picture shows four representations of a carbon dioxide molecule.

Carbon dioxide is a nonpolar molecule. As you can see from the picture above, the molecule is very flat and symmetric. All the electrons that commonly are part of the chemical bondings (valence electrons) are being used.

Carbon dioxide flammability and toxicity

Carbon dioxide is not a fire hazard under any circumstance.

But you still shouldn’t heat a carbon dioxide cylinder, if that’s what you’re asking yourself. It could make the equipment malfunction and facilitate leaking.

Leaking gas cylinders are very dangerous and shouldn’t only be handled by firefighters and similar authorities.

It’s also not exactly toxic but is an asphyxiant gas.

The CO2 content in fresh air varies from place to place, but around 0.041% (410ppm) is estimated. Concentrations of 1% can start making people feel drowsy and make people feel airless.

Concentrations between 7 and 10%, suffocation symptoms appear, and people can turn unconscious. Concentrations bigger than that can kill.

Smaller increases in carbon dioxide concentrations could lead to blood acidification. This can lead to many symptoms, including brain dysfunction that could lead to coma.

But this can’t happen easily. It would require CO2 to be leaking from somewhere, so this risk is only big for professionals that use it in closed and/or unventilated spaces.

Overall, the risks of using carbon dioxide are the same as any compressed gas, but the flammability.


Carbon dioxide is not flammable under any circumstance. No more oxygen can enter the molecule and bond because there is already oxygen in there, which is essentially what normal combustion is. CO2 can be deadly but only under really abnormal circumstances.

Frequently Asked Questions (FAQS): Is carbon dioxide flammable?

Why carbon dioxide is harmful?

You may think that since carbon dioxide is very inert, occurs naturally, and serve as food for plants and microbes, it presents no harm to us.

It’s true that CO2 is not toxic for us directly, but it could lead to blood acidosis if reaches a concentration about 4 times the usual.

But the bigger danger of carbon dioxide is environmental. It’s the most important greenhouse effect agent that can lead to the end of many endangered species, and make agriculture constantly more expansive.

Another 40 billion metric tons of CO2 is added to the atmosphere every year. The carbon dioxide concentration is approaching the mark of 420ppm (before the industrial revolution, it was 270), more than any other period in the whole history of our planet.

Why carbon dioxide is used in fire extinguishers?

The CO2 is inert but helps carry other extinguish agents from the bottle to the fire. Carbon dioxide itself also helps deviate oxygen from the immediate surface of the thing it’s burning.

It also comes cold out of the extinguisher, so it helps reduce the heat that keeps the fire going on. 

Is carbon dioxide polar?

Carbon dioxide is nonpolar. Polarity occurs by an unequal share of valence electrons.

CO2 has a linear and symmetrical structure. The carbon is in the middle, the electron density is being pulled by oxygens (one in the front, one in the back) equally.


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