The gas used in fire extinguishers, as highlighted by the reference, is Carbon dioxide (CO2).
Why Carbon Dioxide is Used in Fire Extinguishers
Carbon dioxide is a highly effective agent for extinguishing certain types of fires primarily due to its unique properties:
- Incombustible: CO2 itself does not burn and does not support the process of combustion.
- Oxygen Displacement: When sprayed onto a fire, CO2 is heavier than air. It forms a blanket over the burning material, displacing or significantly reducing the available oxygen. Since fire requires oxygen to burn, cutting off this supply effectively smothers the flames.
- Cooling Effect: As liquid CO2 is released from the extinguisher and turns into a gas, it expands rapidly and cools the surrounding area, which can also help in extinguishing the fire.
The reference states that Carbon dioxide is stored in liquid form in extinguishers. Upon activation, this liquid is released and rapidly converts back into a gas, providing the necessary volume to blanket the fire.
Types of Fires Suited for CO2 Extinguishers
Carbon dioxide extinguishers are particularly effective on:
- Class B Fires: Flammable liquids (e.g., grease, oil, paint).
- Class C Fires: Electrical equipment fires. CO2 is non-conductive, making it safe to use on live electrical equipment, unlike water-based extinguishers.
Important Note: CO2 extinguishers are generally not recommended for Class A fires (ordinary combustibles like wood or paper) as the material can re-ignite after the CO2 dissipates. They are also ineffective on Class D fires (combustible metals).
Summary Table: CO2 in Fire Extinguishers
| Feature | Description |
|---|---|
| Primary Gas Used | Carbon dioxide (CO2) |
| Mechanism of Action | Displaces oxygen, smothers fire; provides some cooling. |
| Storage Method | Stored under pressure in liquid form. |
| Suitable Fire Types | Class B (Flammable Liquids), Class C (Electrical). |
| Key Properties | Incombustible, does not support combustion, non-conductive. |
Understanding the specific agent used in a fire extinguisher is crucial for selecting the correct type for a particular fire, ensuring safety and effectiveness.
