Fire safety is crucial in any environment, whether it’s your home, office, or a public space. Understanding the types of fire extinguishers available and how they work can save lives and prevent extensive property damage. One of the most common fire extinguishers used for Class A fires is the air pressurized water (APW) fire extinguisher. These extinguishers are highly effective in combating fires involving ordinary combustibles such as wood, paper, and cloth. In this guide, we’ll break down how these extinguishers work, when to use them, and their benefits.
What is an Air Pressurized Water Fire Extinguisher?
An air pressurized water (APW) fire extinguisher is a simple, yet effective, fire-fighting device. As the name suggests, it uses water as its primary extinguishing agent, which is propelled by air pressurized inside the canister. These extinguishers are designed specifically to tackle Class A fires, which involve materials that burn and leave ash behind, such as paper, wood, fabric, and certain plastics.
Key Features of APW Extinguishers
- Extinguishing Agent: Water
- Operating Mechanism: Pressurized air forces the water out of the nozzle.
- Fire Class: Class A (ordinary combustibles)
- Common Locations: Offices, schools, warehouses, and public buildings.
How Does an APW Fire Extinguisher Work?
1. The Science Behind Fire and Fire Classes
To understand how APW extinguishers work, it’s essential to know the basic science of fire. Fire needs three elements to exist: heat, fuel, and oxygen. These elements form the fire triangle. To extinguish a fire, you need to remove one or more of these elements.
- Heat: By cooling the material on fire, you reduce the temperature below its ignition point.
- Fuel: Removing or isolating the fuel can prevent further burning.
- Oxygen: Depriving the fire of oxygen starves it of one of the key components that keep it burning.
Class A fires primarily involve ordinary combustibles like wood and paper, which can be effectively cooled with water. APW extinguishers work by reducing the heat element of the fire triangle.
2. Water as an Extinguishing Agent
Water is an excellent fire suppressant for Class A fires because it lowers the temperature of the burning material, effectively cooling it and preventing it from reigniting. Once the material is cooled below its ignition point, the fire is extinguished. The water also helps absorb heat from the surrounding area, preventing the fire from spreading.
3. Pressurized Air: The Driving Force
The water inside the APW extinguisher is propelled by air that is pressurized to around 100-150 PSI (pounds per square inch). This pressurized air sits on top of the water inside the canister. When you engage the extinguisher, the air forces the water through a siphon tube that leads to the nozzle, where it is sprayed in a controlled stream.
4. Operation: How to Use an APW Fire Extinguisher
Using an APW fire extinguisher is straightforward, but it’s essential to follow the correct steps for effective fire suppression. The common acronym PASS helps guide the process:
- P – Pull the Pin: The first step is to pull the safety pin, which prevents accidental discharge.
- A – Aim the Nozzle: Aim the nozzle at the base of the fire, not at the flames. Hitting the base is critical for extinguishing the source of the fire.
- S – Squeeze the Handle: Squeeze the handle to release the pressurized water.
- S – Sweep Side to Side: Sweep the nozzle side to side across the base of the fire to cover the entire area until the fire is out.
5. When Not to Use an APW Extinguisher
While highly effective on Class A fires, APW extinguishers should never be used on Class B (flammable liquids) or Class C (electrical) fires. Here’s why:
- Class B Fires (Flammable Liquids): Water can spread flammable liquids, making the fire worse.
- Class C Fires (Electrical Fires): Water conducts electricity, posing a serious risk of electrical shock to the person using the extinguisher. Always use non-conductive agents like CO₂ or dry chemicals for electrical fires.
Benefits of Air Pressurized Water Fire Extinguishers
1. Environmentally Friendly
Unlike chemical-based extinguishers, APW units use water, which is a natural, non-toxic extinguishing agent. This makes them an eco-friendly choice, particularly in settings where environmental impact is a concern.
2. Cost-Effective and Easy to Maintain
APW fire extinguishers are relatively inexpensive compared to other types. They are easy to refill with water, and their maintenance typically involves checking for adequate pressure and ensuring the nozzle is clean.
3. Safe to Use
Water is a benign substance for the user and the surrounding environment, making APW extinguishers safe to use in most Class A fire situations. They pose no risk of toxic chemical exposure, which can be a concern with other extinguishing agents.
Limitations of APW Fire Extinguishers
1. Limited to Class A Fires
APW extinguishers are only effective on Class A fires. Using them on Class B or C fires can be hazardous, so having the right extinguisher for the specific fire hazard is essential.
2. Weight and Size
Because they are filled with water, APW extinguishers can be heavier than some other types, making them less portable. This can be a disadvantage in large buildings where mobility is important.
Where Should APW Fire Extinguishers Be Installed?
APW extinguishers are ideal for environments with a high risk of Class A fires. Common locations include:
- Offices and Schools: Paper and wooden furniture pose fire risks.
- Warehouses and Storage Facilities: Wood pallets, cardboard boxes, and packaging materials are potential fuel sources for Class A fires.
- Residential Buildings: Homes with wooden structures or furniture should have APW extinguishers on hand.
Conclusion
Air pressurized water (APW) fire extinguishers are a reliable and environmentally friendly option for tackling Class A fires. By using water to cool the burning material and pressurized air to propel the water, these extinguishers efficiently suppress fires involving ordinary combustibles. However, it’s crucial to use them only for the right type of fire, as they are ineffective and dangerous when used on electrical or flammable liquid fires. Proper knowledge of how APW extinguishers work and when to use them can make all the difference in ensuring fire safety in various environments.