With UK summers becoming warmer, it’s a fair question: can a fire extinguisher left in a hot car explode?
Whether you’re a tradesperson carrying an extinguisher in the van, or a driver who keeps one in the boot for emergencies, it’s important to know the facts.
The short answer is: it’s extremely unlikely—but there are still a few things you should be aware of to store them safely.
Are Fire Extinguishers Safe in High Temperatures?
Fire extinguishers are built to withstand extreme conditions. In the UK, extinguishers that meet BS EN 3 standards are pressure-tested and designed with safety features like:
- Pressure relief valves
- Thick-walled metal casings
- Tamper-proof seals
They’re manufactured to remain stable in a wide range of temperatures—often up to around 50°C or more.
Inside a hot car, temperatures can climb quickly on a sunny day. In rare cases, the inside of a sealed vehicle might hit 50–60°C in direct sunlight. That’s hot, but still within the operating limits of most fire extinguishers.
So no, your extinguisher won’t explode—but there are still a few precautions worth taking.
What Could Happen if It’s Too Hot?
While explosion is highly unlikely, prolonged exposure to high temperatures can:
- Increase internal pressure, putting stress on seals and components
- Cause premature wear of rubber hoses or plastic nozzles
- Affect the reliability of the gauge
- In extreme heat, weaken discharge mechanisms over time
In short, the unit might degrade faster or be less reliable when you actually need it.
If an extinguisher is already damaged or old, then yes—extreme heat could increase the risk of failure. That’s why regular checks and proper storage matter.
Can Any Type of Extinguisher Be Left in a Car?
Different extinguishers handle temperature changes differently:
Powder Extinguishers (ABC)
These are the most common choice for vehicles and commercial vans. They’re:
- Effective on multiple fire types
- Tolerant of wide temperature ranges
- Suitable for use in winter and summer
That’s why powder extinguishers are often fitted in commercial vehicles.
CO₂ Extinguishers
Not recommended for vehicles. CO₂ extinguishers are:
- Pressurised gas cylinders
- Sensitive to extreme heat or cold
- More likely to suffer pressure-related issues in fluctuating temps
Foam or Water
Not ideal for car storage. In winter, they can freeze. In summer, there’s less risk, but foam additives may still degrade if exposed to consistent heat.
Wet Chemical
Rarely used in vehicles. Designed for commercial kitchens. Not suitable for hot or mobile environments.
What’s the Best Way to Store an Extinguisher in Your Vehicle?
To keep your fire extinguisher safe and effective:
- Mount it securely using a vehicle bracket to prevent damage
- Store it out of direct sunlight, ideally in a shaded boot or under a seat
- Avoid leaving it in a sealed box or bag that can trap heat
- Check the pressure gauge regularly (especially after hot spells)
- Don’t leave extinguishers in a vehicle for extended periods unnecessarily
If you run a fleet or regularly store extinguishers in your vans, it’s worth having a routine maintenance schedule.
Legal Considerations
There’s no legal requirement in the UK for private cars to carry a fire extinguisher, but they are required in some commercial vehicles, especially:
- HGVs
- Minibuses and coaches
- Taxis and private hire vehicles (in some licensing areas)
These extinguishers must meet minimum capacity and suitability standards, and should be regularly maintained.
Under The Regulatory Reform (Fire Safety) Order 2005, if you’re a business owner or responsible person for a fleet or site-based vehicles, you must ensure that extinguishers are:
- Properly maintained
- Suitable for the risk
- Accessible and secure
How ESI Can Help
At ESI: Electrical Safety Inspections, we help businesses across Farnborough, Camberley, Reading, Guildford, and throughout Hampshire, Surrey, and Berkshire choose and maintain the right fire extinguishers—including for mobile use.
We can:
- Advise on vehicle-safe extinguishers
- Supply brackets and mounting kits
- Offer annual servicing to BS 5306-3 standards
- Replace or recharge units after use
If you’re unsure whether your extinguisher is safe to store in a hot vehicle—or need help meeting fire safety requirements for your fleet—just get in touch. Our expert team is here to help you stay safe, legal, and prepared.
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