Which cleaning products should never be mixed, and what to do if it happens

The most dangerous combinations are products containing chlorine (sodium hypochlorite) mixed with acidic products such as vinegar, descaler or acidic toilet cleaner, and with products containing ammonia. In the first case, chlorine gas is released; in the second, chloramines. Both gases irritate the eyes, nose, throat and airways. The safe rule is: use only one product at a time, rinse the surface with water between two products, and ventilate.

Why mixing products never helps

People usually mix products with good intentions: they want the toilet cleaner to "work harder", or they add something for limescale to a bucket of water. But the effects do not add up. The substances can react with each other, and instead of a stronger cleaner you get a gas that endangers the person cleaning, as well as other people and pets in the home.

The CDC therefore gives a simple general rule: do not mix products or chemicals together. This also applies to products that seem harmless, and to using two products one after the other in the same place without rinsing.

The risk is higher in small, poorly ventilated spaces. Typically this means a bathroom or toilet without a window, where you bend directly over the bowl, bath or drain while scrubbing. In such a place you can easily inhale even a small amount of gas, so take particular care to ventilate and to use just one product.

Chlorine and acids: chlorine gas is formed

The Washington State Department of Health explains that when chlorine bleach is mixed with an acid, chlorine gas is released. It names toilet cleaners, drain cleaners, rust removers and vinegar as acidic products. With drain cleaners it depends on the composition: the Toxicology Information Centre states that pipe cleaners most often contain alkalis (sodium hydroxide), but these too are corrosive and should not be mixed with anything.

In a Czech household, the typical situations are as follows:

• a chlorine toilet product followed immediately by an acidic limescale gel,
• a chlorine mould cleaner in the shower and a descaler on glass or taps,
• vinegar or citric acid added to water containing a chlorine product,
• two different toilet cleaners poured into the bowl at the same time.

For toilet and sanitary ceramic cleaning products, the Toxicology Information Centre lists sodium hypochlorite and acids as active substances and expressly warns that they must not be mixed with one another, as there is a risk of chlorine gas being released.

For limescale, therefore, use an acidic product on its own, on a different day or after thorough rinsing. The procedure is described in the article How to remove limescale.

Chlorine and ammonia: chloramines are formed

According to the Washington State Department of Health, mixing chlorine bleach with ammonia produces toxic gases called chloramines. In its text on mould, the CDC warns that bleach must never be mixed with ammonia or other cleaning products, because a toxic gas is produced.

Ammonia may be an ingredient of some cleaning products. You can find out whether a product contains it from the ingredients on the label. If you are not sure, simply do not combine products.

What about other combinations?

Chlorine with acids and with ammonia are the best-known cases, but not the only risks. The rule is therefore that you mix nothing that the label does not expressly permit. This also applies to:

• "home" remedies such as vinegar, baking soda or peroxide, if you combine them with commercial cleaners,
• two different drain cleaners poured into the same trap,
• leftover products poured into one bottle to save space,
• a cleaning product added to water in which another product has remained.

The article Cleaning or disinfection explains when disinfection is needed at all and when detergent is enough. The fewer products you keep at home, the lower the risk of mix-ups.

How to recognise a risky product

1. Read the ingredients. Look for the words sodium hypochlorite, active chlorine, acid (citric, formic, phosphoric, amidosulfonic, hydrochloric) and ammonia.
2. Look for warning symbols and statements about hazards and about what the product must not be mixed with. Manufacturers put these warnings on the label precisely for safety reasons.
3. If the label specifies protective equipment, such as gloves or eye protection, use it.
4. If you do not know what a product contains, for example because it has been decanted into another bottle, do not use it with anything else.

Symptoms after inhalation

According to the Washington State Department of Health, chloramines can cause irritation of the throat, nose and eyes, coughing, nausea and breathing difficulties. Chlorine gas irritates the mucous membranes and, at higher exposure, can lead to chest pain, difficulty breathing and fluid in the lungs.

Symptoms may appear immediately, but do not underestimate problems that worsen over time. If your eyes suddenly start to sting or you find it harder to breathe during or after cleaning, stop cleaning and think about which products you have just used and in what order.

What to do if products have been mixed

1. Leave the room immediately and take children and animals out with you. If you can do so without inhaling more fumes, open a window and close the door behind you.
2. Get into fresh air and do not return to the room until it has been thoroughly aired.
3. If you experience coughing, stinging eyes or nausea, call the Toxicology Information Centre: 224 91 92 93 or 224 91 54 02. They will advise on first aid and further steps.
4. If you have difficulty breathing or chest pain, or your condition is getting worse, call the ambulance service on 155.
5. Rinse affected eyes with water. According to the centre, most products, including detergents, are dangerous for the eye, and it recommends rinsing with water for 5 to 10 minutes or longer.
6. If someone has swallowed a product, do not induce vomiting. For common products, the centre advises not inducing vomiting and giving water, milk or tea to drink; however, always discuss the procedure by telephone.

When you call, have the product packaging to hand. The Toxicology Information Centre wants to know the age and approximate weight of the affected person, which product is involved, the amount, the time and manner of contact, and the symptoms.

Safe storage, especially because of children

• Store products out of the reach of children and animals, as the CDC also advises, ideally in a lockable or high cupboard.
• Keep them in their original containers with the label. Never decant them into drink bottles.
• Label diluted solutions with what they contain.
• Store acidic and chlorine products separately so that they cannot mix if spilled.
• Keep washing machine and dishwasher capsules and tablets in a closed box out of the reach of children.

Safe procedure when cleaning a bathroom and toilet

1. Before you start, open a window or switch on the extractor fan, and put on gloves.
2. Choose one product for each task and test it on a hidden spot.
3. Leave the product to work according to the label, then rinse the surface thoroughly with water.
4. If you need a second product, for example for limescale after a chlorine cleaner, use it only after rinsing, preferably at another time.
5. After a chlorine product, flush the toilet several times before using another cleaner.
6. After cleaning, wash your hands and return the products to a safe place.

The same principles apply when removing mould, where chlorine products are most commonly used. You will find more in the article Mould on walls: how to remove it safely.