bleach and gasoline

Chlorine Bleach and Gasoline: A Dangerous Mix, Reaction

I’m sure many of us have heard of such dirty tricks as pouring bleach in an enemy’s gas tank. Many individuals have been charged with a felony after causing serious damage to the vehicle or at least causing the vehicle owner to have their fuel tank pumped out. What happens when you mix bleach and gasoline, and should you ever mix bleach and gasoline? 

The short answer is no since, in the right concentration, the mixture is highly combustible, and it can create highly toxic and deadly chlorine gas. If gasoline is mixed into the fuel tank of your car, don’t turn it on and call your mechanic for next steps. 

The Composition of Bleach and Gasoline

To understand what happens when you mix bleach and gasoline, let’s take a brief look at the key ingredients of each. While many of the reactions are still not completely understood, this will give us some idea of what’s going on.

Chlorine-Based Bleaches

The most common chlorine-based bleaches are based on sodium hypochlorite or calcium hypochlorite.

Sodium Hypochlorite (NaClO)

The active ingredient in most liquid bleach is sodium hypochlorite (NaClO), which is a combination of sodium (Na), chlorine (Cl), and oxygen (O). Sodium hypochlorite forms when chlorine reacts with a solution of sodium hydroxide (NaOH), commonly known as lye (source).

Chlorine, oxygen, and sodium are all highly reactive elements. Chlorine is a halogen, sodium is an alkali metal, and oxygen is an active gas.

When used as liquid bleach, sodium hypochlorite makes a powerful disinfectant and whitener. The chlorine and oxygen atoms break up the double carbon bonds of most dyes, which affects their electrons’ interaction with visible light (source).

Household bleaches usually contain around 3 to 8 percent sodium hypochlorite, while industrial bleach contains 10 to 17 percent (source). The rest of the solution is primarily water with a minor amount of salt to help keep the chlorine in a liquid rather than a gaseous state.

Dakin’s solution is a disinfectant that uses sodium hypochlorite in very small percentages of around 0.5 percent (source).

Calcium Hypochlorite Ca(ClO)2

Calcium hypochlorite or bleaching powder is far more concentrated than your typical liquid bleach and is used to chemically treat swimming pools. A typical container of commercially available calcium hypochlorite contains about 65 percent chlorine.

Gasoline and Hydrocarbons

Gasoline is composed of both aliphatic and aromatic hydrocarbons, while many mixtures now contain some percentage of the alcohol ethanol. Aliphatic hydrocarbons have open-chain structures compared to aromatic hydrocarbons which have circular chain structures.

Aliphatic Hydrocarbons

Aliphatic hydrocarbons can be either saturated or unsaturated hydrocarbons. Saturated hydrocarbons resist further chemical reactions, mainly because their electrons have already been assigned. Unsaturated hydrocarbons are more reactive since they have unassigned electrons in their valence shells.

Alkanes are nonpolar, saturated hydrocarbons, while alkenes are non-polar, unsaturated hydrocarbons. This means that while both have next to no charge, alkenes will accept electrons from other molecules or atoms while alkanes will not.

Alkanes have a single bond between two carbons or carbon and hydrogen, while alkenes have a central double carbon bond. The variants of each share their suffixes –ane or –ene.

Aliphatic saturated hydrocarbons used in gasoline include the alkanes octane, isooctane, heptane, and hexane. The alkane hydrocarbons pentane and butane are used as additives in areas with colder climates.

Aromatic Hydrocarbons

The switch to unleaded gas required the introduction of aromatic hydrocarbon additives such as benzene, toluene, xylene, and naphthalene (source).

Aromatic hydrocarbons are highly stable due to their ring structure. Aromatic hydrocarbons, despite their suffixes, are not alkenes but anulenes and arenes. Benzene, for example, is an unsaturated hydrocarbon with a single carbon bond.

All hydrocarbons are flammable, though their flash points will vary considerably. The flash point of gasoline will depend heavily on its precise chemical composition.

What Happens if You Mix Bleach and Gasoline?

Combining bleach and gasoline will produce a number of dangerous reactions. As a powerful oxidizer, these include combustion, corrosion, and the production of dangerous gases.


Sodium hypochlorite reacts violently with solvents, like acetone, fuels, alcohols, glycols, and insecticides (source). Sodium hypochlorite is not actually combustible on its own, but it is a very powerful oxidizer that enhances the combustion of fuels like gasoline.

A molecule or atom is oxidized when it loses electrons, while a compound that gains electrons is reduced. Oxygen, hydrogen peroxide, and the halogens like chlorine are all oxidizing agents. Both reduction and oxidation occur simultaneously in a redux reaction like combustion (source).

Alkanes like octane are highly reduced while sodium hypochlorite is oxidized (source). A great deal of heat and energy is released during the exchange of electrons, resulting in combustion. A mixture of hydrogen and chlorine will explode if exposed to enough light or heat, resulting in the formation of hydrogen chloride.

Gasoline requires oxygen to burn, and sodium hypochlorite will provide that oxygen. Remember, the formula for sodium hypochlorite is NaClO, so it can readily donate that oxygen atom to hydrocarbons. The oxygen atom will mix with the hydrogen and carbon atoms to form water and carbon dioxide (source).

Combustion is very unlikely to occur with household bleach, which is highly diluted with water, but powdered bleaches with much higher concentrations of chlorine will cause a violent reaction. Chlorine and gasoline should not even be stored together since the mere combination of their fumes can burst into flame (source).

Corrosion and Rust

In higher concentrations, chlorine-based bleach is also highly corrosive, and it can cause irreparable eye and skin damage. Even in lower concentrations, it can cause eye irritation and the burning of the esophagus or gastric lining. When reacting with metal, chlorine causes rust (source).

You should always wash with soap and water after exposure to bleach. You should also make sure to remove any clothing that was contaminated and wash them thoroughly as well.

Production of Dangerous Gases

Halogenated hydrocarbons occur when one or more hydrogen atoms are replaced by a halogen like chlorine. Many halogenated hydrocarbons were used in cleaning products until it was discovered that they caused liver damage and possibly cancer (source). Chlorinated hydrocarbons were also used to produce pesticides like DDT.

The fumes from a burning mixture of sodium hypochlorite and gasoline will be highly toxic, potentially producing chlorinated hydrocarbons like chloroform, dichloromethane, or hydrochloric acid. If there is enough ethanol in the gas, it can also produce chloroacetone or dichloroacetone (source).

Chlorine Gas

As the bleach decomposes, it can form hydrochloric acid (HCl). When this combines with sodium hypochlorite, the result is the highly toxic and deadly chlorine gas.

Chlorine gas was used as a chemical weapon in World War I and was eventually banned by the United Nations. This didn’t prevent and Iraqi insurgents from using it in 2007 (source). Scientists believe that chlorine reacts with the moisture and fats in the human body, causing severe chemical burns (source).

Concentrations of over 400 parts per million (ppm) are fatal when the individual is exposed for over 30 minutes. At 800 ppm, death occurs within a few minutes (sources). Since chlorine gas is twice as dense as air, its vapors will hover at ground level, which made it particularly deadly in the trench warfare of WWI.

Bleach in Your Vehicle’s Tank

While there are YouTube videos out there with individuals driving vehicles with bleach in the tank, it is strongly advised that you do not try this yourself. You will notice that they complain of the smell of bleach in the vehicle, which is very dangerous for their eyes, lungs, and skin.

In most cases, the engine will not start, or it will stall after driving for a period of time. With household bleach, the effect will be closer to having water in your tank since household bleach is mostly water. Industrial bleach will do far more damage and the chlorine may even begin to burn before it gets to the vehicle’s engine.

Felony Charges

Bleach has long been a part of the arsonist’s toolkit, and there have been numerous occasions where individuals have poured bleach into the gas tank of an enemy out of spite. In most cases, this is at least a class D felony.

One recent case in Queensbury, New York, involved a woman who damaged a person’s car by putting bleach and sugar in their vehicle’s gas tank. She was charged with “felony criminal mischief, misdemeanor conspiracy and misdemeanor criminal tampering” after it caused $1,500 in damages (source).

What Do You Do if You have Bleach in Your Gas Tank?

The more chlorine there is in the bleach the more corrosive it will be. It can cause rust in your tank and fuel lines if it remains there, and it can cause damage to the engine if particles of rust reach it.

The small amount of chlorine in household bleach usually doesn’t cause serious harm to the engine unless it is added to the oil. However, the water in the bleach is likely to cause the engine to stall, and this can cause damage to the engine over time.

If you know that you have bleach in your tank, you can prevent the bleach from causing serious damage by flushing out your tank and fuel lines. You can also purchase alcohol-based fuel additives to clean up any residue or sludge.

Removing Your Vehicle’s Fuel Tank

Paying to have your gas tank and fuel lines flushed out can be very expensive. For this reason, there are many who choose to do it themselves.

Lift the Vehicle Securely

If you are able, you may want to drive the vehicle onto a set of ramps. If not, you can lift the vehicle with hydraulic jacks. You may also need an additional jack to safely lower the fuel tank.

Empty the Gas Tank

It will make the job a lot easier if you siphon the gas out of your tank before continuing. Make sure you siphon the fuel into an appropriately designated container. A fluid pump will make the process much easier if you have one.

Detach Cables and Fuel Lines

To prevent the risk of sparks that would ignite the fuel, remove the negative cable from your battery.

Before removing any fuel lines, you will also want to relieve pressure in the lines. The fuel rail on top of your engine will have a fuel pressure regulator on top. If the regulator is vacuum operated, you can remove the vacuum hose from the regulator. You can also use a vacuum pump to empty the fuel lines back into the tank.

Another option is to remove the fuel pump relay and then run the vehicle until the engine until it quits.

Once you have located the fuel tank and the fuel lines, detach the fuel lines, vent lines, and electrical lines. Make sure you have something to catch any fuel that may come out as well, and it will help to have rags or towels handy.

Remove Tank Fasteners

You will then have to remove the fasteners and straps that attach the tank to your vehicle. Again, make sure you have some way to safely lower the tank before attempting this unless your tank pulls up from the trunk. Make sure to consult your vehicle repair manual for the specifics on your tank.

The Fuel Pump

You may need to pull your fuel pump out of your fuel tank. To do so, carefully removed any fuel lines and the lock ring from the top. Very gently rotate the pump left and right before pulling straight up.

Cleaning the Tank

Once the tank has been removed, you can give it a thorough cleaning. You can degrease the tank either with store-bought chemicals or with hot soap and water. Using a pressure washer or a water hose with a high-pressure nozzle, spray out the tank to remove rust and sediment.

For high levels of rust, you will need to use a special cleaning solution. Before attempting to reinstall the tank, make sure you rinse all of the chemicals out thoroughly to prevent damaging your engine. It’s best to let the tank dry overnight.

Waste Disposal

As for the affected gasoline, contact your local waste disposal organization to see where you need to take it.

Removing Your Motorcycle’s Fuel Tank

When disconnecting your motorcycle’s fuel tank, you will also need to separate the petcock, gas cap, and hoses as well as seal the fuel line. Once you’ve separated the fuel line from the carburetor, you can allow the fuel line to drain into an empty container. The remaining steps are very similar to the removal of a car tank.

Purchase a Locking Gas Cap

If you suspect that someone has poured bleach or some other substance in your fuel tank, you may want to consider purchasing a locking gas cap. That way only you can put anything in you fuel tank. Simply keep the key to the gas cap with your vehicle key at all times.

Peroxide-Based and Sulfur Dioxide-Based Bleaches

While chlorine-based bleaches are the most common, there are also peroxide-based and sulfur dioxide-based bleaches. At minimum, these can all cause a vehicle to stall since they contain large amounts of water. Like chlorine-based bleaches, they can also create dangerous gases.

Peroxide-based bleaches are comparatively friendly on the environment since they’re based on oxygen to oxygen bonds, but this also means they’re potent oxidizers. Industrial concentrations of hydrogen peroxide can cause your engine to explode.

Store-bought hydrogen peroxide, on the other hand, has very low concentrations of peroxide and will break down into water and oxygen in your tank if mixed with gasoline. Hydroperoxides actually occur naturally in fuel when it’s allowed to deteriorate over time (source).

Unlike other bleaches that rely on oxidation, sulfur dioxide-based bleaches use a reductive method; they remove the oxygen from colored fabrics and other objects. The effect is only temporary, however, since the atmosphere will naturally reintroduce oxygen to the fabric.

High-sulfur fuels actually produce sulfur dioxide, which is a poisonous gas.

Cleaning Diesel Fuel Tanks

Despite the dangers of mixing chlorinated bleaches with petroleum products, sodium hypochlorite has been used to clean diesel fuel oil supply tanks. Nuclear plants are required to have their own electrical generators onsite, and these are usually diesel generators (source).

The supply tanks for these generators are normally underground, and they have to be cleaned periodically. Sodium hypochlorite solutions are used because soaps or detergents would act as surfactants, allowing chemicals to mix that otherwise would not.

The United States Nuclear Regulatory Commission recommends that other solutions that are equivalent to sodium hypochlorite be used instead to avoid the production of chlorine gas in such enclosed areas.

Final Thoughts

Pouring bleach in someone’s gas tank is no laughing matter since it causes engines to stall and corrodes fuel tanks and lines. Potentially more harmful is the release of chlorine gas.

When high concentrations of chlorine are combined with gasoline, the results can be catastrophic. Chlorine will aid in the combustion of gasoline and produce highly toxic and deadly fumes.

Make sure that you store these chemicals in a safe place away from your home and never anywhere near one another.

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