Which cleaning products are dangerous to mix?

Bleach and ammonia: which products should never be mixed?

The rule to remember is short: never mix bleach with acid-based cleaners or ammonia. It applies whether you pour two products into one bucket, spray them onto the same surface or add one to a toilet bowl that still holds the other.

The National Environment Agency (NEA) sets a wider rule in its list of active ingredients for general disinfection. It says not to mix different disinfectant products, and to use them in a well-ventilated area. The list places household bleach, whose active ingredient is sodium hypochlorite, under active chlorine. NEA also asks you to check each label, use the product according to its instructions and be aware of its potential hazard.

In practice, that means:

• Use one cleaning or disinfecting product at a time.
• Never add a second product to a bucket, spray bottle or toilet bowl to make the first one "stronger".
• If you are unsure what a bottle contains, do not combine it with anything.
• Treat any product labelled as bleach as one that is always used on its own.

Toilet cleaners and bleach

The toilet bowl is an easy place for two products to meet, because whatever you used last may still be in the water or on the rim. Questions about toilet cleaner bleach combinations all have the same answer: one product at a time.

Before you clean the bathroom:

• Read the label of each toilet or descaling cleaner you own.
• If a product is acid-based, or its label warns against mixing, never use it together with bleach.
• Pick one product for the job and use it as the label says.
• Flush and rinse well before you switch to another product, following that product's label.

NEA's guidelines for cleaning and disinfecting residences describe household bleach (sodium hypochlorite) as the most widely used disinfectant and list hypochlorites as fungicidal. NEA also suggests cleaning a bathroom from high to low (wall to floor) and from cleaner to dirtier areas (shower to toilet bowl). If mould is the reason you are cleaning, see how to remove bathroom mould before you start.

Using cleaning products safely

Not mixing cleaning chemicals is the first step. The rest comes from the label and from NEA's guidelines for cleaning and disinfecting residences, which ask you to:

• Prepare and apply a disinfectant according to the manufacturer's guidelines.
• Give it the contact time the product states.
• Use the protective equipment the product's Safety Data Sheet prescribes.
• Ventilate the home during and after cleaning and disinfection, to reduce the concentration of disinfection products in the air.

NEA's list of active ingredients for general disinfection adds two more points: avoid contact with eyes and skin, and keep products away from children. It also notes that alcohols are flammable at high concentration, so keep alcohol-based products away from heat, sparks, open flames and hot surfaces.

At home, that looks like this:

• Open windows and doors before you start, and keep them open after you finish.
• Wear gloves or other protection when the label or Safety Data Sheet calls for it.
• Keep children out of the room while you work.

Storing products

HealthHub's guide to keeping your home free from safety hazards asks you to keep household chemicals such as cleaners, detergents and aerosol cans out of a child's reach. Keep cleaning products in their original containers so children do not mistake them for food, and label poisonous substances with a prominent warning. HealthHub also says not to let a child touch the bottles while you are using cleaning products.

Its page on common childhood injuries and a child-safe home adds that cleaning products should stay in their original containers, never in juice or water bottles. It also suggests looking at your home from a child's point of view, such as the route a crawling baby takes.

For the rest of the home, from window grilles to electrical outlets, work through the childproofing checklist.

If someone is exposed

If a child may have swallowed a cleaning product or another chemical, HealthHub's guide to keeping your home free from safety hazards says to seek medical attention immediately. Do not feed the child anything. Note the time and the substance, so you can tell the medical professional what happened. HealthHub also suggests keeping a first aid kit at home and a list of emergency numbers next to the phone.

A few practical points help in the moment:

• Take the bottle, or a clear photo of its label, so you can name the substance.
• If someone breathed in fumes and feels unwell, get them to fresh air and seek medical attention.

Hiring a cleaner

If you book a cleaner, ask what products the company uses and whether its team brings its own or uses yours. Agree that they will use one product at a time and never mix bleach with acid-based cleaners or ammonia. Show them where your products are kept and mention any you would rather they left alone. For a full disinfection job, see disinfection cleaning. Price depends on the job, so compare home cleaning companies and the prices they publish.

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