A Floating Carbon Monoxide Generator: Toxic Gas Risks on Boats

Toxic gas exposure can occur even when you are relaxing in the fresh ocean air and sunshine on a boat. It is difficult to believe that such a peaceful setting could still present a serious safety risk. Carbon monoxide (CO) is a toxic gas that is odorless, invisible, and non-irritating, which makes it particularly dangerous. Because people cannot see or smell it, they often do not realize it is present until symptoms begin.

Traditional smoke detectors do not alarm for carbon monoxide, which adds another layer of risk in boating environments. Many boaters assume that open air and wind provide enough ventilation, but this is not always the case.

CO is formed anywhere there is combustion. On boats, there are several common sources where this toxic gas can be produced, including:

• Diesel engines
• Gasoline engines
• Gas stoves and lights
• Electrical generators
• Water heaters

Each of these systems produces exhaust gases during normal operation. In enclosed or poorly ventilated areas of a vessel, those exhaust gases may accumulate. Because of this, a vessel can effectively be considered a large floating generator of toxic gas if proper precautions are not taken.

Back drafting is one of the most dangerous ways toxic gas can enter the interior of a boat.

This situation can occur when a boat is operated with the bow at a high angle. Instead of the carbon monoxide exhaust being blown safely away from the vessel, the exhaust gases are pulled back toward the boat. This process, known as back drafting, allows the toxic gas to re-enter the vessel and spread inside.

Once inside, the gas can accumulate quickly and potentially cause carbon monoxide poisoning among passengers.

An illustration of this occurred when a friend of mine and his family went out on grandpa’s favourite lake with his ashes. They slowly travelled around in their boat, reflecting on their loss and sharing memories.

Eventually one of the sons said, “Now let’s gun the boat and spread grandpa’s ashes to the wind.”

When the boat accelerated, the bow lifted high. The ashes were released into the air, but instead of blowing away behind the vessel, they were pulled back toward the boat. The ashes returned inside, covering both the boat and its occupants.

While the story is humorous in hindsight, it demonstrates how airflow around a vessel can behave in unexpected ways. If ashes can back draft into the boat, toxic gas from exhaust systems can do the same thing.

Back drafting is not the only way carbon monoxide exposure can occur during boating.

Other common sources include:

• Swim platforms located close to engine exhaust outlets
• Exhaust fumes from nearby vessels
• Idling engines while passengers sit near the stern
• Poor ventilation in enclosed cabin

Swim platforms are particularly risky because they place passengers close to the point where exhaust gases leave the boat. When a boat is idling or moving slowly, those gases may linger around the stern.

In crowded boating areas, exhaust from other vessels can also drift toward your boat. In these situations, toxic gas exposure may come from multiple directions, not just your own engine.

Another important point is that carbon monoxide does not always need to kill to create danger. In many cases it simply causes dizziness, confusion, or unconsciousness. When boating, losing consciousness can lead to additional hazards such as falling overboard or drowning.

Preventing exposure to toxic gas on boats involves awareness and practical safety measures. Boaters should treat carbon monoxide with the same seriousness as any other onboard hazard.

Key prevention steps include:

• Install marine-approved carbon monoxide detectors
• Maintain engines and exhaust systems regularly
• Avoid idling engines near swim platforms
• Ensure proper ventilation in cabins
• Be cautious when operating at steep bow angles
• Avoid swimming near engine exhaust areas

Passengers should also be aware of early symptoms of carbon monoxide exposure, such as headaches, dizziness, nausea, or confusion. If any of these symptoms appear while boating, it is important to move into fresh air immediately and stop the engine if possible.

Boating is meant to be enjoyable and relaxing, but understanding the risks associated with toxic gas can help ensure that time on the water remains safe for everyone.

References

Lasala, G., McKeever, R., Okaneku, J., et al. “The Epidemiology and Characteristics of Carbon Monoxide Poisoning Among Recreational Boaters”, Clinical Toxicology, 53: 127-130, 2015
Silvers, S.M., and Hampson, N.B., “Carbon Monoxide Poisoning Among Recreational Boaters”, JAMA, 274: 1614-1616, 1995