All About Dry Powder Fire Extinguisher
Also known as ABC extinguishers, dry powder fire extinguishers are quite multi-purpose. They get their other name because they are effective against Class, A, B and C fires. This makes them quite popular. Since most places are susceptible to these three types, the dry powder fire extinguisher is a good choice if you are looking for an extinguisher.
Where to use it?
As explained above, it is effective against Class A, B and C fires. These are:
· Class A – Involving organic material like wood, paper, and fabric
· Class B – Involving flammable liquids like petrol, or paint
· Class C – Involving flammable gases like hydrogen, and methane
Some specialist dry powder extinguishers are also effective against class D fires. The wide scope makes it effective in a wide range of locations, such as homes, offices, factories, boiler rooms, liquid fuel storage, fuel tankers and garages.
How does it work?
To understand this, we have to see how fireworks. For a fire to occur and sustain, we need the fire triangle. The triangle is made of fuel, heat, and an oxidising agent, which is usually oxygen. We need all three conditions to be present for any fire to ignite and carry on. Extinguishers work by breaking the fire triangle, either by rapidly cooling or by suppressing the oxidising agent. It can also do both.
A dry powder extinguisher suppresses the reaction between the three elements of the fire. The chemicals in the extinguisher stop the reaction of the fuel with the heat and the air, thereby stopping the process.
What does dry powder fire extinguisher contain?
- Monoammonium phosphate: It has the ability to flow at 177°C, effectively smothering the fire. This pale yellow coloured chemical is highly corrosive. It is effective against class A fires.
- Sodium bicarbonate: The chemical works by releasing a cloud of CO2 that removes the oxygen, smothering the fire. Effective against class B and C fires, it is not as useful against class A fires. This is because the cloud of gas dissipates quickly. While oil and gaseous fires do not store a lot of heat, fire from solids pack sufficient heat to reignite once the gas dissipates.
- Potassium bicarbonate: Effective against both class B and C, it has a more decisive effect when compared to sodium bicarbonate. It is the preferred agent in oil and gas industry.
- Potassium bicarbonate with Urea Complex: This is the most effective agent in class B and C fires. Its effectiveness lies in its ability to disintegrate into smaller particles, which creates a larger area for the agent to spread.
- Potassium chloride: Developed in the 60s to be protein-foam compatible, potassium chloride has one big disadvantage — it is highly corrosive.
- Foam-compatible: It was developed for fighting class B fires, to be used with protein foams. it is not much in use now.
- MET-L-KYL: This is a type of sodium bicarbonate that is effective against class B and C fires, particularly in case of pyrophoric liquid fires. Apart from sodium bicarbonate, it contains silica gel particles.
How to use it?
Make sure that you are standing at a fair distance from the fire. Aim the nozzle of the dry powder fire extinguisher towards the base of the fire (and not the flames) and squeeze. Move the nozzle in a sweeping motion to cover the maximum surface ares. In case of electrical fires, make sure the power is switched off before using the extinguisher.
- Works on most types of fire.
- It acts quickly, suppressing the fires in seconds
- In case of certain flammable metals, dry powder extinguishers are the only effective agent.
- The gas dissipates quickly. Hence, there is a danger of the fire re-igniting, especially in case of class A fire.
- The powder spreads over a large area and often leaves a residue, which is quite unwelcome. It is also difficult to clean up.
- The powder when discharged can obscure vision.
- The fine powder can be inhaled, becoming a health hazard.
- It should not be used in enclosed areas.
The dry powder fire extinguisher is one of the most versatile extinguisher, effective against class A, B and C fires. But before you buy one, understand its functioning, the type of agents available, its pros and cons.