Bleach

Products referred to as ‘bleach’ usually contain a substance called sodium hypochlorite (NaOCl) in water. This substance can hurt your skin and eyes and it is very poisonous if accidentally swallowed. It is used for disinfecting, (link to disinfectants/antiseptics article) not cleaning, so any kind of dirt needs to be removed with a detergent, not with bleach.

Safe storage of bleach is important because it can decompose in sunlight, on heating or in contact with metals. This decomposition can produce small concentrations of toxic chlorine gas (Cl2) or can lead to acids that react with other cleaning products in dangerous reactions.

As a precaution, it is best to only ever mix it with water. It can be very dangerous when used in combination with many other cleaning products.

Ammonia

Many glass and window cleaners contain ammonia (NH3). It can also be used to remove fat remains from ovens.

Bleach and ammonia should never be mixed. They react to produce chloramines, gases that can cause coughing and breathing problems, as they are toxic. They have the same smell you can feel in swimming pools, because the chlorine disinfectant in the pool can react with compounds in urine or sweat to produce a small quantity of chloramines.

If too much ammonia reacts, an explosive gas called hydrazine can also form. Luckily, this reaction also needs a lot of heat to happen, so it is less likely.

Acids

Some commercial cleaners contain acids like hydrochloric, nitric or phosphoric acids. Solutions of acids are used in sprays for cleaning bathrooms. But other substances you might use, like alcohol or vinegar, are also acids.

Mixing bleach with vinegar or hydrochloric acid can lead to toxic chlorine gas. Chlorine is  dangerous because it forms an acid when it is in contact with wet surfaces, which include your lungs. It irritates your eyes, throat and nose even in small concentrations and can be deadly if too much of it is produced.

Bleach and alcohol can also produce another toxic gas called chloroform. This gas can leave you unconscious if you breathe in too much of it and can also be deadly.

Vinegar should be kept away from peroxide, because the acid that is produced when they mix is very strong. It can give you burns and irritate your eyes and nose.

With baking soda, vinegar can give off some gas, which is carbon dioxide. The other product is water, so mixing these two substances together is not very dangerous, but it will make them less effective at cleaning.

Sodium hydroxide/ caustic soda

This basic chemical is used for removing fat deposits. It can hurt your skin and eyes and its vapours are dangerous to breathe in.

It should not be mixed with any of the acid cleaners, because the reaction can release a lot of heat.

Drain cleaners should also never be mixed, as some of them are acidic and others basic. Giving off heat, the reaction can make the pipes explode.

How can you avoid accidents?

It is important to read the labels of the cleaning products. They should also contain warnings about potential dangers.

If you happen to mix two products and the reaction appears potentially dangerous, because, for example, it is sizzling, bubbling or giving off fumes, a few things can be done. It depends on the circumstances. If there is a small volume of the substances mixed, adding water may help stop the reaction. If vapours are given off, open the window, exit the room and avoid breathing them in. For anything very serious, emergency services should be contacted.