Fire extinguishers contain various extinguishing agents designed to suppress flames by interrupting the fire triangle. The specific agent depends on the type of fire the extinguisher is designed to combat. Common types of agents include water, foam, CO2, and dry chemicals.
Understanding Dry Chemical Agents
Dry chemical agents are among the most widely used extinguishing substances in fire extinguishers. These powders work by interrupting the chemical reaction of the fire and, in some cases, by smothering the fuel source.
Based on available information, key components found in some dry chemical extinguishers include:
- Monoammonium Phosphate: A primary ingredient in multi-purpose dry chemical extinguishers, often referred to as ABC powder. It forms a residue that melts over burning materials, preventing re-ignition (Class A fires) and also works on Class B and C fires.
- Sodium Bicarbonate: Historically significant in the development of dry chemical extinguishers. As noted, Sodium bicarbonate was the original dry chemical extinguishing agent. While potassium bicarbonate (Purple-K) became more effective for certain fires, mixtures based on sodium bicarbonate are still in use.
- Sodium Bicarbonate Mixtures: The chemical currently available is a mixture consisting primarily of sodium bicarbonate with various additives to improve flow and storage characteristics. These additives help prevent clumping and ensure the powder discharges smoothly when needed. Such mixtures are typically effective on Class B (flammable liquids) and Class C (electrical) fires.
Common Dry Chemical Ingredients
Different dry chemical extinguishers utilize specific formulations:
- ABC Dry Chemical: Primarily contains Monoammonium Phosphate. Effective on Class A (ordinary combustibles), Class B (flammable liquids/gases), and Class C (energized electrical) fires.
- BC Dry Chemical: Historically used Sodium Bicarbonate, and modern versions often use Potassium Bicarbonate or Sodium Bicarbonate mixtures. Effective on Class B and Class C fires.
Choosing the correct extinguisher depends on the potential fire hazards present. A multi-purpose extinguisher containing Monoammonium Phosphate is suitable for a wider range of fires (A, B, and C), while those with Sodium Bicarbonate mixtures are effective for B and C risks.
