Extinguishing agent container pressure relief

Fire extinguishing agent containers on aircraft operating under Part 121 must have pressure relief mechanisms to prevent the container from bursting if internal pressure becomes too high. This is a critical safety feature since excessive pressure could cause a catastrophic container failure.

The regulation requires three specific elements:

• A pressure relief valve or device on the container
• A discharge line that vents outside the aircraft where it can be inspected during ground checks
• A visual indicator at the discharge point showing whether the container has released its contents

This setup allows maintenance personnel to quickly determine during preflight inspections if a fire extinguisher container has vented, which would indicate either a pressure problem or that the extinguishing agent has been depleted. Without this external indicator, a discharged container might go unnoticed, leaving the aircraft without adequate fire protection.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*