Most boats have a gasoline or diesel-fueled internal combustion engine. Many also include gas-burning appliances for cooking or heating. Having one or more sources of fuel on board presents a potential danger, especially if you are unaware of leaks or vapor accumulation.
Many boaters have some serious misconceptions about fuel fumes in the bilge or engine compartment.
One is that the engine blower will eliminate dangerous fuel vapors prior to starting a gasoline engine. In fact, any sort of fuel leak can create new fumes as quickly as the blower fan can clear them out, so the risk of explosion is always present, whether the blower is running or not. And although diesel vapors are not explosive, high concentrations can make you sick. One approach is to recognize that any fuel vapor in any part of your boat presents a risk serious enough to warrant the investment in a fume detector. The presence of combustible hydrocarbon vapors causes a change in resistance in the wire, which triggers the alarm.