Carbon monoxide can be a "silent killer," on houseboats and other recreational vessels. It is a colorless, odorless, and tasteless gas that, in high concentrations, can be fatal in a matter of minutes. Carbon monoxide poisoning causes irritated eyes, headache, nausea, weakness, and dizziness. Unless these symptoms are severe, they are often misdiagnosed as seasickness, making carbon monoxide poisoning an under-recognized hazard aboard boats. Although high concentrations of carbon monoxide are deadly, lower concentrations must not be ignored because the effects of exposure to carbon monoxide are cumulative and can be just as lethal.
Carbon monoxide is a by-product of combustion of carbon-based material such as gasoline, natural gas, propane, coal, or wood. Common sources of carbon monoxide aboard boats are the main or auxiliary engines, generators, cooking ranges, space heaters, and water heaters. Carbon monoxide can collect aboard boats in a variety ways: exhaust leaks, improperly vented appliances, entry of exhaust into enclosed areas - most commonly due to mooring too close to a dock or another boat that obstructs the exhaust port, or due to prevailing wind conditions or backdrafts. Previous carbon monoxide warnings and educational materials have concentrated on the hazards created by the exhaust of the main propulsion engines while underway. However, the increasingly common practice of keeping generators running to power air conditioning, entertainment centers, and electronic suites while moored or anchored has added a new dimension to this problem by exposing swimmers and those using outer deck areas in the vicinity of exhaust ports to a potentially lethal environment.
Recently, it was discovered that a number of deaths have occurred on houseboats in which the generator vents into an enclosed space near the stern swim platform. Houseboats with this design are being recalled due to the high concentrations of poisonous gas that accumulate.
The Coast Guard warns all boaters that carbon monoxide poisoning is an extremely dangerous matter that can result in serious injury or death and advises all boaters to ensure that exhaust systems are properly maintained, that appliances are properly vented, that accommodation spaces are properly vented, that swimming areas are properly monitored, and that carbon monoxide detectors are installed in accommodation spaces.