The blue-labelled ABC dry powder extinguisher is rated for Class A solids, Class B flammable liquids and Class C flammable gases. Electrical use is permitted only within the particular product’s marked limits. It is used in some vehicle, outdoor and industrial settings, but visibility and breathing hazards must be considered in its selection.

But powder also comes with the most significant in-use restriction of any extinguisher type: BS 5306-8:2023 specifies that powder extinguishers should generally not be specified for indoor use unless that risk is mitigated through a health and safety risk assessment. That restriction shapes where powder genuinely belongs, and it is the part of the picture most casual guides understate.

This page covers what dry powder does, where it belongs, the Class D specialist variants for combustible-metal fires, and the increasingly important question that catches a lot of people out: dry powder (including L2 powder) is not the answer to a lithium-ion battery fire under the new Class L classification.

What a dry powder fire extinguisher is

A dry powder extinguisher contains a fine, dry chemical powder — usually a salt-based formulation — pressurised with an inert propellant gas (typically nitrogen). The body is signal red with a blue panel near the label. UK capacities range from 1 kg (typically a vehicle unit) up to 9 kg for hand-held workplace units, with larger wheeled units up to 50 kg for industrial sites.

The most common powder is ABC powder, named for the fire classes it tackles — A, B and C. The active agent is usually monoammonium phosphate, sometimes with sodium bicarbonate or other salts. Less common in UK premises but still produced is BC powder, which uses sodium bicarbonate or potassium bicarbonate and is rated for Class B and C only — slightly more effective on flammable-liquid fires but no use for Class A.

Dry powder extinguishers are tested under BS EN 3 and selected and positioned under BS 5306-8:2023. Most UK workplace units carry a Kitemark and a CE or UKCA mark, indicating compliance with the relevant performance and safety standards.

How dry powder works

Dry powder attacks the fire on two mechanisms simultaneously. The powder cloud smothers the fire, physically separating the fuel from the oxygen. At the same time, the chemical decomposition of the powder at high temperature interrupts the combustion chain reaction at a molecular level — the free radicals that propagate the fire are quenched by reaction products from the powder.

What powder doesn't do is cool. Unlike water or foam, dry powder removes very little heat from the burning material. The visible fire goes out quickly, but the fuel stays hot. If there is a continuing source of heat (a hot ember, a shorted circuit, a still-running fuel leak), re-ignition is a real risk after the powder cloud disperses. That is the same operational caveat that applies to CO2.

The lack of cooling is one reason powder is paired with a different type of extinguisher in many premises — a foam unit for Class A, a water mist unit for cooling — even where a single powder extinguisher would be technically sufficient.

What standard ABC powder tackles

Four categories from one unit:

  • Class A (solid combustibles — paper, wood, fabric)
  • Class B (flammable liquids — petrol, diesel, paint, solvents)
  • Class C (flammable gases — propane, butane, methane, LPG); do not extinguish a gas flame unless the supply can be safely isolated by someone competent; do not extinguish a gas flame unless the supply can be safely isolated by someone competent
  • Live electrical equipment only within the particular unit’s marked voltage, distance and operating limits

Electrical suitability depends on the product’s marking and the assessed hazard. A non-conductive agent does not make high-voltage equipment safe to approach. Keep away from substations and damaged electrical installations, call 999 and let specialist responders arrange isolation.

What powder doesn't tackle:

  • Class F (cooking oils and fats). The discharge force can splash burning oil; the powder doesn't interact with the oil chemistry usefully. Wet chemical is the right answer.
  • Class D (combustible metals). Standard ABC powder is not rated for metal fires; a specialist L2 or M28 powder is required (see below).

The 1000 V limit and the 1 m distance

Follow the electrical-use conditions specified for the particular extinguisher. Do not treat a generic 1,000 V claim or a dielectric test voltage as an operating clearance for every powder unit; the agent, equipment and surroundings all matter.

A few practical points:

  • Check the actual product markings and manufacturer instructions; type testing does not mean each individual unit is separately tested on a live fire.
  • Do not infer a safe approach distance from a generic voltage figure. High-voltage installations require authorised specialist response.
  • Where the manufacturer specifies a minimum discharge distance, follow it and the taught operating method. Never approach damaged equipment or enter heat or smoke to make the agent reach.

For more on the wider electrical-fire choice between CO2, dry powder, and water mist, see our guide on the right extinguisher for an electrical fire.

Specialist powder for Class D — L2 and M28

Combustible-metal fires (Class D) need different chemistry. Standard ABC powder is not rated for metal fires, and water and foam react dangerously with several of the metals involved. Two specialist variants exist:

L2 powder is formulated specifically for fires involving lithium metal — the elemental metal, used in laboratory and industrial settings. L2 powder works by smothering the fire and providing a chemical barrier between the metal and the air without the violent reactions that water or standard powder would trigger.

M28 powder is the more general Class D powder, used for fires involving magnesium, sodium, potassium, aluminium swarf and a range of other reactive metals. M28 also works through smothering and chemical inhibition.

Both L2 and M28 are specialist products. They are uncommon in general workplaces and are mostly found where Class D fire risks are explicitly identified — laboratories handling reactive metals, foundries, machine shops working with magnesium alloys. The use of either should follow specific training; they are not equivalent to general ABC powder.

L2 powder is NOT the answer to a lithium-ion battery fire

This is the disambiguation that most matters in 2026, because it catches a lot of people out.

L2 powder is rated for fires involving lithium metal — the pure elemental metal. Lithium-ion battery fires are something different: they involve lithium ions moving between cathode and anode in a self-sustaining electrochemical reaction once the cell goes into thermal runaway. The fuel chemistry, the heat generation mechanism, and the fire behaviour are not the same as a lithium-metal fire.

In January 2026, BS ISO 3941:2026 introduced Class L specifically for fires involving lithium-ion cells and batteries — explicitly noting that no metallic lithium is present. The introduction of Class L was needed precisely because these fires didn't fit cleanly into Class A, Class B, or Class D, and the existing extinguisher options didn't address the unique features (thermal runaway, self-oxygenating reaction, prolonged re-ignition risk).

Three things follow.

Class L describes lithium-ion battery fires in BS ISO 3941:2026. Classification is distinct from evidence that a particular extinguisher can control a particular battery fire. An ordinary ABC or Class D rating does not establish that capability.

L2 powder, despite the name, is not rated for Class L

The "L" in L2 refers to lithium metal, not to the new Class L for lithium-ion. Treating L2 powder as a lithium-ion battery answer is a misreading.

For a lithium-ion battery fire, the practical answer is evacuation

If a battery smokes or catches fire, get out, stay out and call 999. Do not try to move it or use an ordinary powder or CO2 extinguisher as a way to make it safe; thermal runaway and re-ignition need specialist response.

There is more on Class L on our fire classes guide.

BS 5306-8 clause 5.4.3 — the indoor restriction

Powder discharge produces a thick, opaque cloud that drastically reduces visibility within seconds of activation. In an enclosed indoor space, that has three immediate consequences:

  • The user can lose sight of the fire, the escape route, and any other people in the room.
  • The powder is a respiratory irritant; inhalation is unpleasant and, in larger discharges, hazardous.
  • The clean-up afterwards is significant — the powder coats every surface in the room and works its way into electronics, fabrics, and ventilation.

Reflecting all of that, BS 5306-8:2023 (clause 5.4.3) specifically advises that powder extinguishers should not generally be specified for use indoors unless mitigated by a health and safety risk assessment. The wording matters: it is not a flat ban, but it is a strong steer. For most UK workplaces, the practical implication is that indoor primary cover is provided by water for Class A or foam for its marked A/B risks and CO2 (for electrical), with powder reserved for outdoor or specifically-justified indoor settings.

That is why ABC powder, despite being the most versatile single agent, is not the workplace default. The trade-offs land too unfavourably indoors.

Where dry powder belongs

The genuinely good fits for ABC powder:

Garages, forecourts and vehicle workshops

Outdoor or large open-roof spaces, where the visibility issue matters less and where the mix of fuel, vehicles, electrics and gas cylinders all sit within powder's coverage.

Vehicles

Vehicle extinguisher requirements depend on vehicle type, use, carried goods and the assessed risks. A small car unit is not a universal specification for HGVs or dangerous-goods transport, and opening vehicle doors does not eliminate powder’s visibility and breathing hazards.

Boiler rooms and plant rooms — where there is gas (Class C risk) alongside electrical equipment, and where the room is large and ventilated enough that the visibility trade-off can be managed.

Outdoor industrial. Large workshops, construction sites, agricultural buildings — where ABC's versatility outweighs the indoor restrictions.

Less suitable:

  • Offices, schools, hotels, hospitals. Indoor primary cover is better handled by water or foam plus CO2.
  • Server rooms and equipment-sensitive areas. Powder residue will write off the equipment.
  • Confined spaces. BS 5306-8 cautions against both CO2 and powder in confined spaces; powder additionally creates a respiratory and visibility hazard.

How to use a dry powder extinguisher

The PASS technique applies — Pull, Aim, Squeeze, Sweep — with two powder-specific notes:

  • Stand back. The powder cloud reduces visibility within seconds, and once you can no longer see the fire, you can no longer aim. Use the particular unit’s operating distance and trained method; withdraw if visibility, heat or smoke threatens your escape.
  • For a Class B liquid fire, sweep rapidly across the surface. For Class A solids, focus on the base of the fire and aim slightly low to ensure powder reaches the burning fuel.

Discharge duration varies by product. Use only the trained method and withdraw if the initial application does not control the fire; do not stay in smoke or lose your escape route.

For the full step-by-step, see our PASS technique guide.

Servicing

Conventional powder units normally need at least monthly visual checks, annual basic servicing and a five-year extended service. Primary-sealed designs can have a different interval. Use a competent maintainer; BAFE SP101 is one certification route. See our servicing guide.

One powder-specific watch-point: the powder can compact over time, particularly in vehicles and outdoor units exposed to vibration and temperature change. Annual service includes a check to ensure the powder is still free-flowing. A unit with caked powder will not discharge correctly when needed and must be reconditioned or replaced.

Frequently asked questions

Can dry powder be used indoors?

Generally not, unless the risk has been mitigated through a health and safety risk assessment. BS 5306-8:2023 (clause 5.4.3) advises against indoor use because of visibility loss, respiratory irritation, and clean-up. Indoor primary cover in UK workplaces is more usually provided by foam or water plus CO2.

What's the difference between L2 and M28 powder?

Both are specialist Class D powders for combustible-metal fires. L2 is formulated specifically for lithium metal fires. M28 covers a wider range of reactive metals — magnesium, sodium, potassium, aluminium swarf and others. Neither is rated for Class L (lithium-ion battery) fires.

Can I use a dry powder extinguisher on a lithium-ion battery fire?

Class D and lithium-ion battery hazards differ. L2 powder is intended for specified metal fires, not proof of suitability for battery thermal runaway. If a battery smokes or burns, leave and call 999.

What electrical-use limits apply to dry powder?

There is no safe generic rule that switches from powder to CO2 above 1,000 V. Follow the particular product’s marking, and do not approach high-voltage equipment. Isolation and response require appropriately authorised specialists.

What is ABC powder?

The most common UK dry powder formulation, rated for fires of Class A (solids), B (flammable liquids), and C (flammable gases), with electrical use permitted only within the particular unit’s marked limits. The active agent is usually monoammonium phosphate. Standard for vehicles, garages, forecourts and outdoor workshops.

What's the difference between dry powder and CO2 for electrical fires?

Both are non-conductive and rated for live electrical equipment. CO2 is residue-free, making it the better choice indoors and around sensitive electronics. Dry powder is more versatile (covers Class A, B and C as well) but produces a visibility-reducing cloud and a difficult clean-up. Outdoor electrical fires often suit powder; indoor fires usually suit CO2.

Where this connects

For the deeper electrical-fire decision, see our guide on the right extinguisher for an electrical fire. For the flammable-liquids context, see our flammable liquids fire guide. For where dry powder sits in the wider type and colour system, the fire extinguisher types hub is the right starting point. The Class L disambiguation is covered more fully on our UK fire classes guide.

If you are responsible for fire safety provision in a UK workplace, the online fire safety awareness training course covers what every employee needs to know, in 90 minutes.

Sources & references

Official guidance and standards checked on 15 October 2026.

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Mark McShane
Mark McShane
Health & Safety Training Specialist, Online CPD Academy

Mark writes about workplace health & safety, fire safety and accredited online training for Fire Safety Awareness Training, part of Online CPD Academy.