An all in one dry powder fire extinguisher can deal with a variety of different fire classes. These extinguisher types are arguably the most versatile, and there are very few fire types that they cannot be used to control.
They can be used on electrical equipment fires, burning metal fires, fires involving flammable liquids, and are commonly carried as car fire extinguishers to name a few. However, dry powder fire extinguishers have some limitations and are only safe to use in specific situations.
Find the Right Powder Fire Extinguisher
How Do Dry Powder Fire Extinguishers Work?
Dry powder fire extinguishers target the ‘oxygen’ side of the fire triangle.
They do this by forming an effective powder barrier between the oxygen in the air and the chemical processes between the ‘fuel’ and ‘heat’ sides.
Once released, this fire extinguisher releases an inert solid powder over the targeted area. As the solid lands on the source of the fire, it forms a layer over the top. This prevents oxygen from reaching the heat and fuel and eventually extinguishing the fire.
What Do Dry Powder Fire Extinguishers Contain?
The solid powder in this extinguisher type comes in the form of sodium bicarbonate, potassium bicarbonate, or sometimes mono ammonium phosphate.
The specific powder used often differs depending on your extinguisher supplier but generally has a yellow appearance.
Although non-toxic, the dry powder found in a powder fire extinguisher can be detrimental to the user’s health, particularly if inhaled. Once sprayed, the powder can also cause impaired vision or skin irritation.
You’ll also find a non-flammable, compressed gas inside a powder fire extinguisher. This gas sends the powder out of the nozzle when the lever is pulled.
What Is A Dry Powder Fire Extinguisher Used For?
Powder fire extinguishers are versatile in that they can control 3 of the main fire-type combustibles:
- Solid combustibles
- Liquid combustibles
- Electrical equipment combustibles
However, the big drawback of powder fire extinguishers is that they cannot be used in enclosed spaces, as the powder can impair both sight and breathing if discharged in an enclosed space. This may make putting out the fire even more difficult and nearly impossible to escape an out-of-control fire.
For this reason, you are unlikely to find one in an office, a school, or any confined space.
What Type Of Fire Is A Dry Powder Extinguisher Used For?
Powder fire extinguishers are referred to as multi-purpose fire extinguishers and also dry chemical fire extinguishers.
This extinguisher type is commonly found in workshops, industrial plants, or anywhere that features a big, expansive space or easy access to an outside area.
These fire extinguisher types can also be called ABC fire extinguishers because they can be used for Class A, B, and C fires.
Class A fires
Powder extinguishers can be used on an array of fire types, including Class A fires.
These fires are caused by combustible, solid materials, including paper, wood, textiles, and some light plastics.
Class B fires
Unlike simple water fire extinguishers, powder fire extinguishers use dry materials to put out. This means that combustible liquids cannot be further spread around.
For this reason, powder extinguishers can be used on flammable liquids, such as paint, petrol, and diesel, which each cause Class B fires.
See Also: Petrol fire extinguisher guide – a look at the 3 different types of extinguisher (including foam) that can be used on burning fuel.
Class C fires
It’s safe to use powder fire extinguishers on Class C fires. These include fires involving butane, methane, hydrogen, and other combustible gasses.
Like all fire types, Class C fires require oxygen to survive, and dry powder fire extinguishers safely and effectively seal off the fire from the oxygen.
Class D fires
Specialist dry powder extinguishers are the best and only recommended option for Class D fires. This fire category relates to the burning of such metals as titanium, potassium, and magnesium.
Again, because the combustion substance is solid, it does not cause the heat and flames to spread in any way, which allows it to put the Class D fire out effectively.
Electrical fires
Dry powder fire extinguishers can be used on fires involving electrical equipment. But they are not as effective as a CO2 fire extinguisher.
If the electrical equipment involved is over 1000v, for example, a dry powder fire extinguisher will be ineffective. Plus, dry powder fire extinguishers do not cool fires, which means there’s a chance the electrical fire could reignite.
What Not To Use Powder Extinguishers For?
Despite the extinguisher type’s versatility, dry powder fire extinguishers cannot be used on all fire types.
Specifically, they cannot be used on the following fire types:
Class F fires
A dry powder fire extinguisher should not be used on a cooking fire involving grease or cooking oil.
To effectively put out a Class F fire, not only does the oxygen supply need to be cut off, but the fire also needs to be cooled down. Dry powder fire extinguishers cannot cool down fires, so they are unsuitable for taking on a Class F fire.
The only fire extinguisher type that’s suitable for dealing with a Class F fire is a wet chemical fire extinguisher, which works to both cool down the flames as well as cut off the oxygen supply.
Fires in Enclosed Spaces
No matter the fire type, a dry powder fire extinguisher should not be used in enclosed spaces.
Once sprayed, the powder can make it difficult for those nearby to see and can cause severe health problems if inhaled.
What Colour Is A Powder Fire Extinguisher?
Dry powder fire extinguishers come in the standard red extinguisher cylinder and can be identified from the other extinguisher types by a blue-coloured label.
This label will read ‘POWDER’ in white capital letters. The label side of the extinguisher should also read ‘powder extinguisher’ somewhere on it.
See Also: Fire Extinguisher Colours guide – a look at how to identify extinguishers via the colour coding system.
How To Use A Powder Extinguisher
Despite their extra capabilities, dry powder fire extinguishers work just like any other extinguisher.
To use, follow these instructions, but only if the fire is small enough to get under control. If the fire is gaining size rapidly, concentrate on evacuating the building and contacting the fire and rescue service.
Step 1 – Remove the safety pin
Remove the safety pin on the dry powder fire extinguisher to break the seal. This will allow you to discharge the powder kept inside freely.
Step 2 – Cut off the power
When dealing with electrical fires, make sure to cut the power off before releasing the powder. Conversely, when extinguishing a gas fire, be sure to cut off the gas. In both instances, only do so if it’s safe.
Step 3 – Aim the nozzle
Always aim towards the base of the fire. In the case of liquids, start at one side of the fire with the intent of discharging powder across to the other side of the fire. In the case of electrical fires, point and discharge the powder directly at the fire.
Step 4 – Discharge the powder
The best way to discharge the powder depends on the type of fire you’re dealing with.
- For solid materials, start at the base and slowly move across the rest of the fire.
- For electrical fires, keep pointing at the flames until the fire is extinguished.
- For flammable liquids, start at one side of the fire and gradually sweep over the flames.
- For gas, aim to extinguish the flare before tackling the rest of the fire.
Final Thoughts
Dry powder fire extinguishers may be the most versatile fire extinguisher on the market, but it comes with limitations.
Not only is it one of the messiest fire extinguishers around, but it’s also very dangerous to use, while use in confined spaces is totally off-limits.
Still, if used responsibly, a dry powder fire extinguisher can put out fires related to electronics, flammable liquids, gas, and solid materials efficiently and safely.
Further Reading
- Legal requirements for fire extinguishers in the workplace – An easy to read guide on the regulations on extinguishers.
