Narrative:

During engine start; first flight of the day; the aft cabin fire extinguisher began to discharge halon. Not from the emitter but from the junction of the bottle and the high pressure regulator. The flight attendant; who was walking by doing her pre-departure checks; heard the leak; saw the halon; and used blankets to contain the gas. Returned to the gate and opened forward cabin entry door. The halon had dissipated by then and; without a replacement extinguisher; the passengers were deplaned. Probably dissimilar metal corrosion between the bottle and high pressure valve combined with a cold night created enough of a gap in the seal. Remove the valves from the bottles and inspect the tolerances. The hydrostatic test may not be sufficient. This failure takes the aircraft out of service.

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Original NASA ASRS Text

Title: B737 Captain reported a cabin fire extinguisher leaked out all its pressure.

Narrative: During engine start; first flight of the day; the aft cabin fire extinguisher began to discharge Halon. Not from the emitter but from the junction of the bottle and the high pressure regulator. The Flight Attendant; who was walking by doing her pre-departure checks; heard the leak; saw the Halon; and used blankets to contain the gas. Returned to the gate and opened forward cabin entry door. The Halon had dissipated by then and; without a replacement extinguisher; the passengers were deplaned. Probably dissimilar metal corrosion between the bottle and high pressure valve combined with a cold night created enough of a gap in the seal. Remove the valves from the bottles and inspect the tolerances. The hydrostatic test may not be sufficient. This failure takes the aircraft out of service.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.