Fire Extinguisher Basics: Parts, Fire Classes and Monthly Checks

Most of us walk past the red cylinder on the wall every day without really looking at it. Spend two minutes with it now. Below we go through its parts, the fire classes printed on its label, how to use it and the quick monthly checks that tell you it will work. If a fire is more than small and just starting, do not fight it. Leave and call 101 or 112.

What an extinguisher can do

An extinguisher is for the first minute or two of a fire, while it is still small. Used then, by someone who knows how, it can stop a dustbin fire or a smouldering switchboard from turning into a house fire. That only works if you have the right type, you know how to use it and it has been looked after.

The parts of a fire extinguisher

Every portable extinguisher has the same few parts. Know what each one does and you will know what to check.

• Safety pin and tamper seal: the pin locks the lever so the extinguisher cannot go off by accident. If the seal is broken or the pin is missing, it may have been used or tampered with, so get it checked.
• Operating lever: squeezing it releases the extinguishing agent.
• Hose and nozzle: this is what you aim at the base of the fire.
• Pressure gauge: where there is one, the needle should sit in the green. Too low or too high means it needs servicing.
• Cylinder: look for dents, rust or leaks.
• Label: it tells you the type, the fire classes it is meant for and how to operate it. Read it now, not on the day of a fire.

Fire classes

Fires are grouped by what is burning. Indian Standards use five classes, and the label on your extinguisher shows which of them it can handle.

• Class A: ordinary solids such as wood, paper, cloth and plastics.
• Class B: flammable liquids such as petrol, diesel, oil and wax.
• Class C: flammable gases under pressure, such as LPG and propane.
• Class D: burning metals such as magnesium, sodium and titanium.
• Class F: cooking oil and fat in cooking appliances, at home or in a commercial kitchen.

In India, live electrical equipment is not a separate class. It adds a shock risk to the fire, so switch off the power if you can do it safely.

Types of extinguisher

• Water: for Class A fires. Water cools the burning material.
• Foam: for Class A and B fires. Foam forms a layer between the fuel and the air and smothers the flames.
• Carbon dioxide (CO2): for Class B and C fires, and commonly used on electrical equipment because it leaves no residue. CO2 pushes out the oxygen the fire needs.
• Dry chemical powder (ABC): for Class A, B and C fires. The powder interrupts the chemical reaction of the fire.
• Wet chemical: made for Class F fires. It reacts with burning cooking oil and fat to form a soapy layer that puts the fire out and stops it flaring back.

Never use a water extinguisher on burning oil or on live electrical equipment.

How to use it: PASS

1. Pull the pin to unlock the lever.
2. Aim the nozzle or hose at the base of the fire, where the fuel is burning.
3. Squeeze the lever to release the agent.
4. Sweep the nozzle from side to side over the fire.

Stay calm and keep your exit behind you. If the fire is spreading fast, the smoke is building or you are not sure what is burning, get out and call 112 (or 101 for the fire brigade).

Once you know the parts and the fire classes, our fire extinguisher chooser can tell you which type suits your own kitchen, shop or office.

Monthly checks

• Gauge: the needle should be in the green. Too low or too high means it needs servicing.
• Body: look for dents, rust, corrosion or leaks.
• Pin and seal: both should be in place. A broken seal means it may have been used or tampered with.
• Hose: no cracks, and nothing stuck in the nozzle.
• Service date: refill and service as the label and your service agency require. Some extinguishers also need a periodic pressure (hydrostatic) test of the cylinder.

Today, find the nearest extinguisher at home or at work, read its label and check that the needle is in the green. If anything is stacked in front of it, move it.