Problem - The risk of accidental explosion in gasoline powered small craft is well known. Onboard propane heating and cooking systems can present the same hazard. Gasoline powered vessels must be fitted with an adequate ventilation system that efficiently removes explosive vapors from engine bilge spaces and fuel track compartments to prevent serious problems. Propane fuel systems need to be properly maintained and fuel tank compartments vented to the outside. Failure to follow these safety precautions can lead to spectacular consequences.
History - Resolution of the fuel vapor problem was historically a boat operator's responsibility. Boat manufacturers took on some additional responsibility to provide small craft ventilation systems beginning in 1940. Most of these systems were designed to take advantage of natural airflow patterns to remove harmful vapors. In the United States, the Coast Guard did not mandate powered ventilation systems in boat engine compartments until after 1980. Powered ventilation systems use a arrangement of vent cowlings, hose ducts and a blower motor to remove explosive vapors form enclosed spaces. There was even some discussion of requiring an ignition switch interlock with the engine blower in the development of the new regulations. Eventually objections from boat manufacturers prevented this idea from being implemented.
Operation of Powered Ventilation Systems
– Earlier boats that utilize natural ventilation require that the owner properly maintain the installed equipment. The engine compartment should be inspected regularly for potential fuel leaks. Boats built after 1980 will have an installed power ventilation system onboard for each engine compartment equipped with a remote cranking or starter motor. The powered system will consist of an exhaust blower, an exhaust duct, and an intake duct located in the lower third of the engine space and kept above normal bilge water levels. A placard should be installed at the operators' position that reads:
Warning: Gasoline vapors can explode. Before starting engine, operate blower at least 4 minutes and check engine compartment bilge for gasoline vapors.
Make sure ventilation system opening are kept clear, duct hoses are intact and untorn, and that the blow operates correctly. Replace worn parts with marine grade products. Boat owners are responsible for keeping ventilation systems in safe operating condition.
Explosion Prevention Measures - There are several other strategies you can employ to prevent fire or explosion on your vessel:
- Review the standards for Safe Fueling
- Check the condition of engine backfire flame arrestor on carburetor equipped boats
- Ask the Coast Guard Auxiliary for a Vessel Safety Check
- Have propane fuel connections checked for leakage prior to boating season
- Consider installation of a Propane Fume Detector
Alan Sorum - Alan Sorum is the Maritime Operations Project Manager for the Prince William Sound Regional Citizens' Advisory Council (PWSRCAC). Alan is ...
