Which two extinguishing agents are most commonly used in engine compartment fire extinguishing systems?

The most commonly used extinguishing agents in engine compartment fire extinguishing systems are Halon 1211 and Halon 1301. These agents are effective through their ability to interrupt the chemical reaction of combustion within the fire triangle (heat, fuel, and oxygen), making them particularly suitable for aviation applications.

Halon 1211 is a known effective extinguishing agent for class B and C fires, which include flammable liquids and electrical fires, both of which can occur in an engine compartment. Halon 1301 is used for total flooding systems, providing protection for larger compartments where the entire volume needs to be saturated with the extinguishing agent to ensure that no part of the fire remains.

The extensive use of these agents in the aviation industry stems from their low toxicity and effectiveness at extinguishing fires quickly without causing additional damage to sensitive equipment, which is critical in engine compartments where electronic components may be present. Additionally, Halon was favored due to its non-corrosive nature and ability to extinguish fires without leaving residue.

Alternatives like foam or CO2 are also used in certain contexts, but they are not as commonly employed in engine compartments as Halon formulations. Foam can be ineffective for certain types of fires, especially in a confined