Fire extinguishers are essential for protecting people and property in the event of a fire—but what about the chemicals inside them?
Are they safe to use around people, or do they pose a health risk?
This is a common concern, especially for businesses that want to ensure both fire safety and occupant wellbeing.
The short answer is: most fire extinguisher agents used in the UK are not toxic when used correctly—but some can cause irritation or require cleanup precautions.
What’s Inside a Fire Extinguisher?
There are several types of fire extinguishers commonly used in UK homes, workplaces, and public buildings, each containing a different extinguishing agent.
The main types include:
- Water and water mist
- Foam (AFFF – Aqueous Film Forming Foam)
- Powder (ABC dry powder or specialist Class D powders)
- Carbon dioxide (CO₂)
- Wet chemical (for cooking oil/fat fires)
Each of these agents behaves differently and comes with its own set of health and safety considerations.
Water and Water Mist Extinguishers
These are the safest and least hazardous extinguishers. They contain nothing but water (or deionised water in mist versions), and they leave no residue. There’s no toxicity, making them ideal for offices, schools, shops, and homes.
Some may have small additives to improve performance, but these are not considered harmful under normal use.
Foam Fire Extinguishers (AFFF)
Foam extinguishers are very effective for Class A and B fires (solid combustibles and flammable liquids), but they can leave a slippery residue that may need cleaning up.
Older foams used PFAS (per- and polyfluoroalkyl substances), which have raised environmental and health concerns. Modern foams used in the UK are increasingly fluorine-free or low in persistent chemicals.
Direct skin contact with foam should be avoided, and inhaling the mist in enclosed spaces could cause mild irritation. Foam is not considered highly toxic, but wash off any residue and ventilate the area after use.
Powder Fire Extinguishers (ABC)
Dry powder extinguishers contain a fine chemical powder, usually monoammonium phosphate or sodium bicarbonate. While not classified as toxic, powder extinguishers:
- Can cause eye, skin, and respiratory irritation if inhaled or exposed
- Create a lot of dust that can be difficult to clean
- May cause issues with electronics and delicate equipment
Powder extinguishers are not recommended for indoor use in occupied areas unless absolutely necessary. They’re best suited for outdoor use, vehicles, or industrial settings.
CO₂ Fire Extinguishers
Carbon dioxide extinguishers are often used for electrical fires. They don’t leave residue, but they do displace oxygen, so there’s a risk of asphyxiation if used in a confined or poorly ventilated space.
The cold discharge can also freeze skin on contact (frostbite risk). While CO₂ itself isn’t toxic, misuse can be hazardous. Always point the nozzle away from people and ventilate the area after use.
Wet Chemical Extinguishers
Used mainly in commercial kitchens, wet chemical extinguishers contain potassium salts in a water-based solution. They work by cooling the oil and forming a soapy layer to smother the fire.
While not highly toxic, the mist can cause irritation to the eyes and respiratory tract. Prolonged skin contact should be avoided. Clean any surfaces thoroughly after discharge, especially in food preparation areas.
Are Fire Extinguisher Chemicals Safe After a Fire?
Even if the extinguishing agent itself is considered low in toxicity, any residue may combine with soot, burnt materials, or fumes from the fire. So proper cleanup, ventilation, and PPE (personal protective equipment) are recommended after using any extinguisher.
In some commercial environments, such as server rooms or laboratories, specialist clean-agent systems (e.g. inert gases like Novec or FM-200) may be used to avoid chemical or powder contamination altogether.
What the Law Says
In the UK, all fire extinguishers used in commercial premises must meet BS EN 3 standards and be maintained in line with BS 5306-3. Manufacturers are required to provide Material Safety Data Sheets (MSDS) for each extinguisher type, which include any health risks and recommended handling precautions.
If you’re not sure what extinguishers you have—or what’s best for your setting—a fire risk assessment will help guide the correct, safe choice.
How ESI Can Help
At ESI: Electrical Safety Inspections, we support businesses across Farnborough, Camberley, Guildford, Reading, and throughout Hampshire, Surrey, and Berkshire with expert fire extinguisher advice, installation, and servicing.
We can:
- Identify the best extinguisher types for your premises
- Check your current units for safety, suitability, and service status
- Provide MSDS and training on safe use
- Ensure your extinguishers meet all UK fire safety regulations
If you have concerns about the safety or health impact of your fire extinguishers, speak to our team. We’ll help you stay protected—without compromising the safety of your people, property, or environment.
