Is Chlorine Dioxide Flammable?

This article will answer the following question “Is Chlorine Dioxide Flammable?”. We will also unveil the nature of this compound and understand how it can be hazardous.

Is Chlorine Dioxide Flammable?

Chloride dioxide is not flammable, but it can cause a fire because it can decompose itself without oxygen, irradiating a lot of energy in the form of heat, so it’s potentially explosive as well. Chloride dioxide enhances the flammability of other substances.

What is Chlorine Dioxide?

Chlorine Dioxide is a strong oxidant and broad-spectrum biocide.

It is used for the treatment of drinking water, in the bleaching of wood pulp, as a disinfectant in several industries, and in textile bleaching.

Chlorine dioxide (ClO2) is a simple molecule. It has an atom of chloride bonded with two oxygen atoms, so it ain’t much chemically stable and can decompose violently in high concentrations, hence its strong oxidizing capabilities.

In 2020, Chlorine dioxide kits started being sold as a remedy under various names, especially Miracle Mineral Solution (MMS), as a cure for many diseases, including Covid, and HIV. Even kids had received chlorine dioxide enemas as a supposed cure for autism.

But not only ingestible chlorine dioxide has no health benefits for us, but it is also known that the product presents acute toxicity that can lead to death if swallowed.

Chlorine Dioxide Chemistry

To explain chlorine dioxide dangers and hazards we must first unveil some important scientific concepts.

Chlorine Dioxide (ClO2) is a molecule made of three atoms. One chloride and two oxygens. 

Atoms are one of the smallest particles that have mass. There are about 118 different atoms that we know in the universe. Anything we can grab is made of atoms and energy.

Stars, supernovas, cosmic dust, bread, water, screwdrivers, and ourselves are examples of things that are made essentially from the same atoms (but not all of them), they are just arranged differently.

When atoms bond with other molecules, grant different properties to them. Every molecule behaves in a certain way due to the atoms it has within, and how these atoms interact with the exterior. 

Chloride and oxygen are normally molecules that wish to steal and retain electrons from others (oxidize them). Bonded together, these atoms have a whole new set of properties, but the ability to steal electrons remains. This is why chlorine dioxide is called an oxidizer.

Oxidation is one of the means a disinfectant works. Although, it is also how fire works. Oxidation is the process of losing electrons.

It might sound too simple, but nearly anything in chemistry is due to the fact that some entity has lost electrons for another.

When an oxidizer bleach is applied to a contaminated surface, the bleach steals electrons from the microorganism, which is the first domino piece to fall down that will lead to disinfection.

When a source of fuel, let’s say, a piece of wood burns, it’s because the oxygen in the air reacted with the carbons and hydrogens from the wood, stealing electrons/ oxidizing the wood hydrocarbons. 

Chlorine Dioxide Flammability

Chlorine dioxide is not combustible, nor flammable. But it doesn’t mean that there’s no fire hazard when dealing with it.

As we saw in the previous topic, burning is a specific kind of oxidation, one that happens with oxygen. About 21% of our air is made of oxygen gas (O2), which is one of the reactants in a combustion reaction. 

Let’s take a look at two combustions (the hydrogen and propane gas burning). The arrow means is changed into.

The combustion of hydrogen gas(H2):

2H2 + O2 → 2H2O + energy

The combustion of propane gas (C3H8 ):

C3H8 + 5O2 → 3CO2 + 4H2O + energy

As you can see, the initial compounds react with oxygen, and oxygen becomes part of the byproducts. We can say that when a fire happens, a source of fuel changes into something else, and this something else has oxygen within. 

The energy is nothing more than heat and light, it is the visible part of a fire. Before a burning starts, the fuels have a lot of energy stored in the form of chemical bondings between the atoms. 

After the burning, the byproducts have just a little energy because they are very simple molecules. So where is that energy now? That energy is what we see in a fire. Is the heat that moves our cars, industries, that cooks our meals, and makes us feel warm. 

Those two chemical equations above are not simply ways to write the reactions down, they are expressing that everything there’s in one side of the arrow must be in the other as well. No atom is lost in a chemical reaction, nor does the energy.

But let’s get back to the chlorine dioxide flammability

So, chlorine dioxide can burn or not??

Well.. No. Chlorine dioxide (ClO2) already has oxygens on its molecule, and no more can get in. It’s profoundly impossible for it to burn under normal circumstances.

Chlorine dioxide is already oxidized, so it can’t burn. Just like water, carbon dioxide, and many oxides out there.

Remember when we said that energy is stored in the chemical bondings of molecules? Chlorine dioxide is a molecule that has a lot of energy within it. It’s also unstable, which is why it must be kept cool and in an aqueous solution.

A little heat is capable of making chlorine dioxide decompose itself. But this decomposition is not ordinary, it liberates a lot of energy in a short time, so there’s also a risk of explosion. 

Chlorine dioxide can’t catch fire, but it produces heat naturally during decomposition. Because of that, it enhances the combustion of other substances and can never get in contact with sources of fuel.

ClO2 is a potential fire hazard, even though it cannot catch fire.

Safety data sheets

You can check further important information regarding chlorine dioxide in their safety data sheets (SDS).

SDS are documents made by authorities that compile much useful information about the safety of the products.

This one dates from 2005 but has a lot of useful information about the substance complied.

This is very concise. It shows some overall fire prevention measures, fire fighting, and more.

Here you can see a SDS for a specific chlorine dioxide solution, from a brand named ERCO Worldwide LP.

This one is about chlorine dioxide in gas form. It specifically says that “Chlorine dioxide does not require air for it to burn”, as we saw earlier.


Chlorine dioxide can’t possibly burn because it can’t participate in a combustion reaction, but can still be a fire hazard. The compound can suffer thermal degradation in mild conditions, liberating a lot of heat without any need for air, which can lead to an explosion.

Frequently Asked Questions (FAQS): Is Chlorine Dioxide Flammable?

Is chlorine dioxide bleach?

It is used as bleach, but not all bleaches contain chlorine dioxide. It is not normally allowed for domestic use because it might be toxic for us, and can be a fire hazard.

Is chlorine dioxide heavier than air?

Yes, chlorine dioxide is heavier than air, so it can accumulate in low-lying areas and enhance the possibility of an explosion.

Is chlorine dioxide safe for dogs?

No animal should ingest chlorine dioxide, it is not safe for dogs and could lead to death. The compound is used for purifying water among other things, but the consumer doesn’t really drink the compound once it evaporates and decomposes later on. 

Disinfectants work because they’re applied directly to microorganisms. If an animal swallows chlorine dioxide or uses it in an enema, the compound will be in touch with the organs, not the infection. 

Chlorine dioxide also turns into gas easily and can do a lot of damage from the inside.


Ganiev, I. M., Timergazin, Q. K., Kabalnova, N. N., Shereshovets, V. V., & Tolstikov, G. A. (2005). Reactions of chlorine dioxide with organic compounds. Eurasian Chemico-Technological Journal, 7(1), 1-31.

Gordon, G., & Rosenblatt, A. A. (2005). Chlorine Dioxide: The Current State of the Art. Ozone: Science & Engineering, 27(3), 203–207. doi:10.1080/01919510590945741

What was missing from this post which could have made it better?

Leave a Comment