I. Common Types of Fire Extinguishers and Their Applications

Dry Powder Fire Extinguishers

Mechanism: Works by smothering flames with a dry chemical powder that isolates oxygen and inhibits the chemical chain reaction of combustion.

Suitable For: Class A (solid combustibles), B (flammable liquids), C (flammable gases), and electrical fires involving energized equipment.

Typical Use Cases: Ideal for initial fire response in homes, offices, vehicles, and general multi-risk environments.

Carbon Dioxide (CO₂) Fire Extinguishers

Mechanism: Discharges high-pressure CO₂ gas to displace oxygen around the fire and cool the burning material.

Suitable For: Class B and electrical fires, especially where cleanup or residue is a concern.

Typical Use Cases: Critical for protecting sensitive areas like laboratories, server/computer rooms, electrical switchgear rooms, and archives containing valuable documents or equipment.

Foam (AFFF) Fire Extinguishers

Mechanism: Forms an aqueous film foam blanket that seals the surface of the burning material, cutting off air supply and cooling the fuel.

Suitable For: Class A and B fires (especially flammable liquids like oils, petrol). Not suitable for water-miscible liquids (e.g., alcohols, esters) or electrical fires.

Typical Use Cases: Commonly deployed in kitchens, garages, workshops, and fuel service stations where liquid fuel fires are a risk.

Water-Based (Water Mist) Fire Extinguishers

Mechanism: Cools the fire with a fine water mist and can create a vapor barrier that helps shield the user from radiant heat.

Suitable For: Class A fires (ordinary combustibles like wood, paper, textiles). Not suitable for electrical, Class B (liquid), or Class F (cooking oil/fat) fires unless specifically rated.

Typical Use Cases: Suitable for homes, schools, and offices where the primary fire risk involves common solid materials.

II. Operating Instructions

General Usage Steps (P.A.S.S. Technique):

Pull: Pull the safety pin or clip to break the tamper seal.

Aim: Aim the nozzle or hose at the base of the flames, maintaining a safe distance of 2-5 meters.

Squeeze: Squeeze the operating lever or handle to discharge the agent.

Sweep: Sweep the nozzle from side to side across the base of the fire until it is extinguished.

Special Operational Notes for Specific Types:

CO₂ Extinguishers: Always grip the insulated horn (discharge wand) to avoid direct skin contact with the extremely cold metal parts. Ensure adequate ventilation after indoor use to prevent oxygen displacement.

Foam Extinguishers: For stored-pressure types, simply operate normally. For older chemical foam types requiring inversion, follow manufacturer instructions carefully. Avoid aiming the jet directly into a burning liquid pool to prevent splashing.

III. Key Precautions

Storage and Maintenance:

Store extinguishers in easily accessible, visible locations away from direct sunlight, excessive moisture, or extreme temperatures.

Perform regular visual inspections. Check the pressure gauge monthly (for dry powder and stored-pressure types) or weigh CO₂ cylinders periodically. Replace or service immediately if the needle is outside the green zone or weight loss exceeds specifications.

Usage Prohibitions:

Never spray against the wind, as the extinguishing agent may blow back towards you.

For electrical fires, attempt to de-energize the equipment first if safe to do so. Use only extinguishers specifically rated for electrical fires on live equipment.

Do not use foam and water extinguishing methods simultaneously on the same fire, as this can reduce effectiveness.

Critical Safety Reminder:

Personal safety is paramount. If a fire cann