What is used as a fire extinguishing agent in some older aircraft?

What is used as a fire extinguishing agent in some older aircraft?

• A. Hydrogen peroxide.
• B. Water mist.
• C. Foam concentrate.
• D. Carbon dioxide (CO2).

Answer: (D)

Carbon dioxide is used in some older aircraft because it extinguishes a fire by blanket-smothering it and displacing the surrounding oxygen in enclosed compartments. When CO2 releases, it rapidly fills the space around the fire, reducing the concentration of oxygen available for the flames and interrupting the combustion process. It’s effective for engine compartments and electrical/fire-hazard bays where a quick knockdown is needed and where residues from other agents would be undesirable, since CO2 leaves no residue that could damage equipment. This method is most practical in sealed or semi-sealed areas where the fire is contained and access for firefighting personnel is limited. However, it's hazardous to crew or passengers in occupied spaces because it can cause asphyxiation, so these systems are designed to discharge in unoccupied or isolated sections. Other agents have drawbacks for older aircraft: hydrogen peroxide isn’t a standard onboard extinguishing agent and can be corrosive or hazardous; water-based mist can risk damage to electronics and systems in older airplanes; foam concentrate is heavy and leaves residues that can contaminate systems and require cleanup. Carbon dioxide offers a rapid, clean extinguishing effect in confined compartments, making it a practical choice for certain older airframes.

Carbon dioxide is used in some older aircraft because it extinguishes a fire by blanket-smothering it and displacing the surrounding oxygen in enclosed compartments. When CO2 releases, it rapidly fills the space around the fire, reducing the concentration of oxygen available for the flames and interrupting the combustion process. It’s effective for engine compartments and electrical/fire-hazard bays where a quick knockdown is needed and where residues from other agents would be undesirable, since CO2 leaves no residue that could damage equipment.

This method is most practical in sealed or semi-sealed areas where the fire is contained and access for firefighting personnel is limited. However, it's hazardous to crew or passengers in occupied spaces because it can cause asphyxiation, so these systems are designed to discharge in unoccupied or isolated sections.

Other agents have drawbacks for older aircraft: hydrogen peroxide isn’t a standard onboard extinguishing agent and can be corrosive or hazardous; water-based mist can risk damage to electronics and systems in older airplanes; foam concentrate is heavy and leaves residues that can contaminate systems and require cleanup. Carbon dioxide offers a rapid, clean extinguishing effect in confined compartments, making it a practical choice for certain older airframes.