Fire Extinguisher Myths Answered

We asked Anthony Buck BSc (hon) CMIOSH MIFPO, who is a Qualified Extinguisher Service Technician and one of the most knowledgeable fire extinguisher experts we know to write us a post about a few fire extinguisher myths.

This ‘FAQ’ document sets out to dispel incorrect information often given to uses about fire extinguishers by suppliers/maintainers/health & safety staff

1. Fire extinguishers must be replaced after 10 years

Answer – No

There is no statutory maximum service life for a fire extinguisher. Some bodies recommend a 20 year limit, but in practice an extinguisher can continue in service indefinitely whilst:

  • Parts remain available
  • The extinguisher has no damage, defect or corrosion rendering it unsafe for use
  • It is not an Obsolescent type (see below)
  • It is serviced, including extended services and for CO2 statutory overhaul, as required

2. If a fire extinguisher hasn’t been serviced for a few years it must be replaced

Answer – No

It just means that a service is all the more urgent. As long parts are available and it passes it’s basic, extended service or overhaul (as required) and is not Obsolescent it can continue to be used

3. Old colour coded extinguishers are obsolete and must be replaced.

Answer – No

Many pre BS EN3 extinguishers still have suitable spares & parts available and can continue in service as long as in serviceable condition.

4. Fire extinguishers must be replaced at their 5 yearly Extended Service interval as it’s not cost effective to carry this out

Answer – No

What they mean is it’s too time consuming for them to carry out this test & they’d rather just replace it. The actual cost of carrying out an extended service is less than replacement, particularly for water and foam types – the actual ‘cost’ price in parts & refills to Extended Service a water extinguisher is less than £5.

5. Stainless steel/polished finish extinguishers are illegal

Answer – No

Although they cannot be kite marked to BS EN3 due to their colour, they remain perfectly legal as long as new models are CE marked; and are preferred where aesthetics are important. A competent fire risk assessment can justify their use, normally where signage & staff awareness is in place.

6. CO2 extinguishers must have a 5 year extended service

Answer – No

For a short time around 2000 the servicing standard BS 5306-3 did require this, but after feedback from manufacturers this was removed in the 2003 revision as not required or of value

7. CO2 extinguishers must be replaced after 10 years

Answer – No

It may be more profitable and less time consuming for the engineer to do this, but what is required at 10 years is an Overhaul, which includes a hydraulic pressure test of the cylinder (to meet requirements of Pressure systems legislation) and new valve. An overhaul is better for the environment, recycling an existing cylinder and cheaper than a new extinguisher, which only has 10 years before overhaul anyway – there is no longer a lifespan advantage.

8. Every ‘kitchen’ requires a fire blanket and powder extinguisher

Answer – No

Extinguisher provision is risk based and most ‘kitchens’ in premises are just tea points with kettle, microwave, dishwasher, etc. A fire blanket is not needed if there is no small Class F risk, i.e. no cooker with hobs that a chip pan or frying pan could be used on. A powder extinguisher is not very effective on enclosed electrical equipment such as microwaves and causes severe secondary damage and CO2 is more appropriate. Full working kitchens will require Wet Chemical extinguishers if fryers are in use.

9. Fire extinguisher service personnel are experts

Answer – No

The fire trade is sales driven and there are no requirements to hold any qualification in extinguisher maintenance or, as important, to attend refreshers. For every competent engineer there are several who are unqualified or cut corners, or will use any excuse to sell new equipment. Care must be taken when choosing a provider and should you require to know your extinguisher requirements a competent fire risk assessor is a more unbiased source of advice.

10. Is my extinguisher engineer servicing my equipment properly?

Answer – Maybe yes, maybe no

Corners are sometimes cut to save time/money or through ignorance. Some staff just ‘shine & sign’, a term for wiping the extinguisher down so it looks like it’s been attended to and filling in the label. Things to look for:

If any of these activities were not done and the original extinguisher remains, then they are not correctly serviced. Likewise not performing an extended service at the correct interval is also negligent.

Label terminology: A correctly completed service label should include:

  • Date (year and month)
  • Type of service- Initial, Basic, Extended, Recharge or Overhaul. NOT obsolete terms such as Serviced (S), Inspected (I), Discharge Test (DT) which suggest a lack of refresher training.
  • Weight in kg
  • Next extended service or Overhaul date
  • iv. Other checks. Many other factors can be checked by suitably trained auditors such as the author of this guide

11. What genuine reasons for condemning an extinguisher exist

Answer – Even correctly serviced equipment will deteriorate to an unsafe condition and reach end of life. The only reasons are:

  • i. corrosion, wear or damage to threads of any pressure retaining part
  • ii. corrosion of welds
  • iii. extensive general corrosion or severe pitting;
  • iv. significant dents or gouges in the body
  • v. fire damage to the body or body fittings
  • vi. any split in a plastics lining, or any significant bubbling or lifting from the metal of a plastics lining
  • vii. corrosion of the metal body under a plastics lining
  • viii. corrosion of the metal body under a zinc or tin/lead lining
  • ix. overpainting or application of any other coating, film or colouring to any plastics component that could be subject to pressure
  • x. UV degradation of plastics components
  • xi. illegible marking or operating instructions
  • xii. instructions not in English

12. What genuine reasons for replacing an extinguisher due to Obsolescence exist?

Answer – Eventually an extinguisher will become obsolete for a variety of reasons, usually relating to availability of parts, ineffectiveness or safety concerns. Types included are;

  • i. chemical foam extinguishers
  • ii. soda acid extinguishers
  • iii. extinguishers with a riveted body shell
  • iv. extinguishers with a plastics body shell
  • v. extinguishers that require inversion to operate
  • vi. non-refillable extinguishers that have reached their expiry date
  • vii. extinguishers for which parts are no longer available and servicing cannot be completed
  • viii. halon extinguishers (prohibited by statute)
  • ix. extinguishers manufactured after 2002 which do not carry a CE mark This excludes refurbished extinguishers (see Note).NOTE Refurbished extinguishers cannot carry the CE mark and cannot be condemned for not carrying it.
  • i. All new extinguishers require Commissioning by a competent person. This has been introduced due to the growth in internet sales. Often extinguishers are supplied to users in their original factory cartons and are not fully assembled. This has led to extinguishers in use that were defective or dangerous due to incorrect or non assembly by unqualified users and difficulties I ongoing maintenance due to vital information about the extinguisher’s age, mass, etc not being recorded
  • ii. A tolerance of +/- 1 month is given for annual Basic Servicing, so that a few weeks delay in a service visit is no longer a non conformity
  • iii. Due to it being impossible to determine if a plastic headcap has suffered internal cracking from impact or degradation from UV light or chemicals unless it fails during discharge (a safety risk), extinguishers with such headcaps must have them replaced at ever 5 year Extended Service. Some service companies for their convenience will suggest total replacement, but in reality for the many models where the parts are still available it is cheaper for the user to simply replace the headcap
  • iv. Additional safety reasons to condemn an extinguisher – see ix to xii in Paragraph 12 above
  • v. Additional extinguishers that cannot be serviced due to Obsolescence/Nonconformity – see ix in Paragraph 13 above
  • vi. A more detailed description of the requirements to become a Competent Person

KFC – Keep Frying correctly

Frying tonight – the ‘f’ class fire classification

Over 10 years ago a new classification of fire was introduced for fires involving cooking oils, however there is still some ignorance around the need to have specialised equipment to safely tackle fires in this category and many establishments remain unprotected against this dangerous fire risk


For fire fighting purposes fires have been classified, first under BD 4547 and now EN2, according to the main type of fuel involved.

Class A – fires involving flammable solids

Class B – fires involving flammable liquids and liquefiable solids

Class C – fires involving flammable gases

Class D – fires involving flammable metals

Class F – fires involving cooking oils and fats

There used to be a Class E for electrical fires, but this was discontinued as electricity doesn’t burn – an electrical fire can involve any of the above classes, with the presence of electricity being an additional hazard rather than a fuel. Fires where electricity are present are still categorised separately on extinguisher labels so that a non-conductive agent that is safe for use where a live electrical supply is involved can be identified.

Cooking oils and fats were traditionally part of Class B, along with substances like petrol and spirits. However a major difference in how they burn means that normal agents for Class B fires are ineffective. Most flammable liquids, such as petrol or heptane (which is used for fire test rating of Class B extinguishers), burn around 50 degrees Centigrade. However, cooking oil fires commonly start when the oil is heated to past it’s auto-ignition temperature, usually between 285 & 385 degrees Centigrade, but sometimes up to 499 degrees Centigrade. The oil burns at this temperature, but it’s auto-ignition temperature is reduced (by this burning) by about 30 degrees Centigrade. Thus, the fire will be self sustaining unless it’s temperature is significantly reduced. This high temperature makes the fires very dangerous and presents problems when trying to use normal extinguishing methods on these fires. A tble at the end of this article summarises the problems with traditional agents.

Case studies

The following case studies illustrate the problem when using traditional agents.

  1. South Mimms Service Area – A fast food restaurant’s fryer caught fire and was immediately tackled with CO2 extinguishers. These had no effect and the fire spread to the ductwork. The entire service area burnt down as a result.
  2. Heathrow Terminal One – A fast food restaurant’s fryer caught fire and was immediately tackled with CO2 extinguishers. These had no effect and the fire spread to the ductwork. The terminal was severely damaged. Millions of pounds were lost through damage and disruption.
  3. Royals Shopping Centre – A fryer caught fire in one of the units and was immediately tckled with two fire blankets. One was too small, the other burnt through. Despite the rapid attendance of the fire service and the use of a fixed BC Powder extinguishing system the fire was only just contained with great difficulty.

Following lobbying by the fire industry, Class F, a new fire classification, was introduced for all fires involving cooking oils.

A new symbol for use on extinguishers, depicting a burning frying pan with the letter F in the top right corner, was also introduced.

The only type of extinguisher to be Class F rated is the Wet Chemical extinguisher. This contains an alkaline liquid solution of up to 20% potassium salts (potassium acetate, potassium citrate, potassium carbonate) and it is the unique effect of these salts on the fats in cooking oils that is the key to their effectiveness.

Wet Chemical saponifies the oil, i.e. by hydrolysis rapidly converts the burning substance to a non-combustible soap. This process is endothermic, meaning it absorbs thermal energy from its surroundings, decreasing the temperature and eliminating the fire. The soapy scum formed also secures vapours and generates steam, assisting the extinction further.

Even a raging fryer with 75 litres of oil can be extinguished in under 2 seconds, however the entire extinguisher must be discharged onto the oil to ensure a complete crusting of the surface and maximise cooling.

Potassium salts had been used in the US for many years in the form of ‘loaded stream’ extinguishers for greater effectiveness on Class A fires and it was the US who developed the first Wet Chemical extinguishers for cooking oil fires in the 1990’s

Chubb Fire first introduced US made Badger Wet Chemical extinguishers to the UK in the late 1990’s, followed by the UK base of the US firm Amerex and currently there are several manufactures of these extinguishers around the world.

In the UK Wet Chemical extinguishers are made to BS 7937: 2000 and are identifiable by a Canary Yellow panel to the front of the extinguisher and the class F symbol. They bear a Fire Rating based on the maximum size, in litres of oil, the extinguisher can extinguished when used by a skilled operator. A typical 6 or 9 litre extinguisher would be rated 13A:75F (the water base makes it suitable for Class A fires as well)

Because they discharge as a fine mist they pass the 35kv conductivity test for extinguishers and can be used in the presence of energised electrical equipment, although care needs to be taken with pools of agent on the floor.

The cost of the agent makes them slightly dearer than traditional extinguishers and to make them available to smaller establishments are produced in a range of sizes with ratings from 25F to 75F. The German manufacturer Total has a compact 2 litre model with an impressive 40F rating.

Comparison of agents

Extinguishing media Effectiveness on Class F fires
Light duty fire blanket BSEN1869 Only tested and effective on small cooking oil fires up to 3 litres and containers of no more than 345mm diameter.Difficult to apply as requires getting close to the fire. Can eventually burn through or sink into the burning oil
Water/water additive Water mixes with the fat, boils and the steam ejects burning fat
Aspirated Foam Branchpipe Used to be used in kitchens, not commonly available now. Requires skilled application and high delivery rates as the extreme heat destroys the foam blanket
Foam Spray The extreme heat breaks up the extinguishing film preventing it sealing off the fire
CO2 The gas is readily dispersed by the air currents produced by the raging fire and the lack of cooling action means the oil remains at auto ignition temperature
ABC Dry powder (Acidic Ammonium Phosphate) In virtually all current powder extinguishers. Being acidic cannot saponify the oil and although the flames may be temporarily knocked down the oil reignites as the extinguisher runs out
BC Dry powder (alkaline sodium bicarbonate) Used to be used in most powder extinguishers and does have some effect, but requires several larger extinguishers and there is a re-ignition risk
Halon 1211 BCF Illegal except for exempted special users.


This is a guest post from Anthony Buck of

Anthony’s knowledge of UK fire extinguishers and the Regulations is unsurpassed

FE-36 Clean Agent

With the worldwide ban on Halon 1211, the race was on to create a clean, safe alternative for use in highly sensitive areas. As a result, the US manufacturing giant DuPont created FE-36, or Hydrofluorocarbon-236fa (HFC-236fa).

FE-36 works almost as effectively as the illegal halon, is less toxic, and does not deplete the ozone layer. FE-36 also leaves no residue, is non-corrosive, non-conductive, and will not cause thermal shock damage to machinery.

How Fire Extinguishers Containing DuPont FE-36 Work

These extinguishers discharge a stream of gas and liquid droplets that are propelled into the heart of the fire, stopping combustion through a chemical reaction and by absorbing the fire’s heat.

Since FE-36 becomes a gas at -1.4 degrees C (39 degrees F), it leaves no residue behind and after the fire, dissipates into the atmosphere. FE-36(tm) fire extinguishers can be used on fire classes A and B, and directly on electrical equipment.

FE-36 Fire Extinguishers in Europe

Although not yet widely available in the UK and Europe, these extinguishers are used in medical facilities across the USA. In addition, portable fire extinguishers containing FE-36 can be used in sensitive locations such as computer rooms, document stores, clean rooms, telecommunications facilities, control rooms, switch rooms, marine craft and installations, banks, museums, archives, laboratories, and airplanes.

The most common range of fire extinguishers containing FE-36 are Cleanguard extinguishers from Ansul.

In the UK Today

Motorsport participants might also be interested in the Zero 360, an FE-36 extinguisher especially for high performance racing and rally cars from Lifeline.

Also seen in small automatic extinguishers, the defunct Firemaster company’s previous management have set up a new company called Fireblitz Extinguisher and are now supplying 1kg and 2kg automatic sizes again.

“Total Flood” Fire Suppressant Systems

DuPont FE-36 can now be used to replace Halon 1301 in fixed fire protection systems. Fire extinguisher systems with FE-36 come into their own where a ‘total flood’ fire suppressant system is required. This involves ‘flooding’ an entire room or enclosed area with sufficient fire fighting agent to extinguish the fire. (If CO2 gas were used instead, the volumes involved would prove fatal to anyone in the area.)

FE-36 and Hydrogen Fluoride

When combusted, under certain conditions, FE-36 can produce hydrogen fluoride (HF). Whilst this gas is generally produced in small quantities, and the gas itself boils just below room temperature, you should make sure that after a fire, the area is fully ventilated before staff return.

You should also avoid breathing in any fumes from an FE-36 extinguisher treated fire, as on contact with moisture, including human tissue, hydrogen fluoride converts to hydrofluoric acid. This acid is highly toxic and corrosive.

MRI-Safe Fire Extinguishers

MRI-safe fire extinguishers are designed to protect these expensive and life-saving machines from damage in the event of a fire. High specification CO2 fire extinguishers and water mist extinguishers are designed with non-magnetic components to be able to operate in the vicinity of a magnetic resonance imaging (MRI) machine.

How MRI-Safe Fire Extinguishers Work

MRI-safe fire extinguishers are essentially the same as normal extinguishers on the inside. However, MRI-safe fire extinguisher cylinders must be non-magnetic, as the magnetic field of an MRI machine is strong enough to attract a normal fire extinguisher with bone-crushing force.

It is not often realised but the magnetic potency of an MRI machine stays for a long time after it is turned off. This prevents fire-fighters from entering with something as simple as a metal belt buckle. There have been incidents of people being “sucked” into an MRI with tragic results.

The same rule applies to any machinery with a strong magnetic field, such as nuclear magnetic resonance spectrometers (NMR’s). Non-magnetic fire extinguishers should also be used in health centres, clinics, and any premises where magnetic interference might affect the performance or operation of sensitive equipment.

Non-magnetic fire extinguishers are made with a non-magnetic stainless steel or aluminium shell, and non-magnetic fittings such as valves, nozzles and pins.

Specially manufacturerd 2kg CO2 fire extinguishers are the most popular non-magnetic type in the UK, since they can be used to extinguish fires in, on or around electrical equipment, are clean to operate and do not leave any residue after use. The non magnetic fire extinguisher is available online from Fire Protection Online and is made by Chubb Fire (and also sold under their sister company name of Thomas Glover).

Water Mist Fire Extinguishers

Amerex Corporation of the USA developed their water mist extinguisher for use in clean rooms, telecoms areas and health care facilities. Using distilled water instead of tap water, it has a specially-developed misting nozzle that atomizes the water making it non-conductive.

These are available in 1.75 gallon and 2.5 gallon size and as a 9 litre size in the UK (model 272) BAFE approved to BS EN3. They have UL approval in the USA.

As you can imagine, high specification non-magnetic fire extinguishers do not come cheap, retailing at a premium to the standard models. But, they can be found online at much lower prices.

Know Your Extinguishers

In the event of a fire, using the correct extinguisher to put it out is as important as discovering the fire itself. All modern fire extinguishers are clearly marked as to the type of fire they should be used on, so you can tackle small fires safely and easily.

Different Fires Require Different Fire Extinguishers

It sounds obvious, but different types (or classes) of fire require different extinguishers. For example, a water-based extinguisher is ideal for use on free-burning materials such as paper or wood, known as a Class 1 fire. For full details, see our in-depth guide to fire extinguisher types

UK Fire Extinguisher Markings and Colours

All fire extinguishers are colour coded for easy recognition in an emergency. They also have ratings as to which class of fire they can be effective in extinguishing, so you can double-check that you have the right fire extinguisher for the job.

In addition all fire extinguishers should bear quality standard marks, such as the familiar BS Kite Mark and CE Mark. For full details on classes of fires and extinguisher ratings, see the detailed guide to fire extinguisher fire ratings and multi-rating fire extinguishers

A Fire Extinguisher in the Hand

A fire extinguisher is only truly effective when you, the person picking it up in an emergency knows the best way to use it! Our handy guide to how to use a fire extinguisher takes you through simple steps for efficient fire extinguisher use.

Fire Extinguisher In-depth Guides

The best and clearest fire extinguisher information, right here at your fingertips.