What is the proper way to extinguish an induction system fire that occurs when starting a reciprocating engine?

• A. Shut off the engine and evacuate the area.
• B. Use a CO2 extinguisher directed into the carburetor air inlet immediately.
• C. Stop the engine and cut fuel flow, then try to restart.
• D. Keep the engine running, which will blow the fire out. If this does not work, use a CO2 fire extinguisher directed into a carburetor air inlet.

Answer: (D)

When an induction system fire starts during engine start, the aim is to use the engine’s airflow to push the flames out of the intake and keep the fire from spreading. Keeping the engine running creates a strong air stream through the carburetor air inlet, which tends to blow the flames away and out of the induction path. If the flames don’t die out with the air blast, a portable CO2 extinguisher directed into the carburetor air inlet can blanket the fire and smother it by reducing the available oxygen.

Shutting off fuel or stopping the engine can trap fuel in the induction and may allow the fire to intensify or reignite when restarted. Starting again while flames are present risks feeding the fire back into the engine. Evacuation isn’t typically the first step once you can safely control the fire, and using the extinguisher immediately without attempting to use the engine’s airflow isn’t as effective as leveraging the induced air blast first.