Carbon Monoxide Poisoning and Prevention

Carbon Monoxide (CO) is a deadly gas that enters the body through the lungs and cuts off oxygen to the body within minutes, resulting in death. This substance is colorless, odorless, and tasteless; even in minimal quantities, it is highly toxic. 

CO poisoning causes immediate symptoms once it has been inhaled. Some of these symptoms are similar to the flu, such as headaches, fatigue, and nausea. CO can enter a cabin in several ways, such as from a water heater, a stove in the kitchen, appliances that run on gas or propane, or even from boats nearby. Many die yearly due to CO poisoning in boats or around boats. Almost all of these fatalities or injuries are preventable. Boat operators must become familiar with carbon monoxide and its poisoning prevention practices.

two boats docked, with one suffering from carbon monoxide spill

Boaters must idle their engines only in well-ventilated areas to minimize the risk of CO poisoning. All fuel-burning engines or appliances on a watercraft must be approved for marine use.

The following are safe practices that can contribute to the prevention of CO poisoning:

  • Cooking and heating only in well-ventilated areas
  • Inspecting the engines and generators for leaks in the exhaust system
  • Providing regular inspection and maintenance for the boat 
  • Taking necessary actions when the marine-rated CO detector alarms 

Exhaust Leaks

In boats, exhaust leaks are the most common cause of CO fatalities. A leak in the exhaust system allows CO to travel throughout the boat and into enclosed spaces. 

Despite proper venting of the exhaust, some circumstances can cause it to flow back into the watercraft. Among these circumstances are when two vessels are moored close together, when a fuel source is running on the boat while it is idle, and when the load on the boat causes the bow to rise.

There is also a risk of exhaust leaks occurring during cruising under certain conditions, mainly when a canvas is in place, resulting in the “station wagon” effect. Exhaust may also collect in enclosed spaces near the stern swim platform. Thus, swimming near the stern of the watercraft while engines or other CO-producing devices are operating is particularly hazardous.

Death Zones to Avoid


“Teak” Surfing involves holding on to the swim platform of a boat while it travels slowly through the water, surging in its wake. This hazardous activity places the passengers near the boat’s propeller. Due to this, passengers will be exposed to highly intoxicating amounts of CO produced by the watercraft’s exhaust. 

man teak surfing


Gas can readily be trapped in and around exhaust vents through swim platforms. It is NEVER permissible to enter an enclosed area under a swim platform. 

Carbon Monoxide Checklist
1. Conduct a performance test on each carbon monoxide detecting device in the boat. 
2. All exhaust clamps should be appropriately positioned and secured.
3. Check for any leaks from system components, which can be detected by corroded fittings, water leaks, rust, or black streaking on the exhaust.
4. Check the rubber exhaust hoses for burnt or cracked sections and ensure they are free of kinks.
5. Check the exhaust sound for any changes, as they may indicate a malfunctioning component.
6. Ensure that cooling water flows from the exhaust outlet when the generator and engine run.

IMPORTANT: During the pre-trip inspection, the vessel should not be operated if any problems are identified. Before running the boat, it should be investigated further by a qualified mechanic.

The Proper Way To Deal With Suspected CO Poisoning:

symptoms of carbon monoxide poisoning

It is crucial to take immediate action if a boater or passenger exhibits symptoms of CO exposure, such as headaches, irritated eyes, dizziness, weakness, or nausea. Despite similar symptoms, CO poisoning should not be confused with intoxication or seasickness.

When poisoning symptoms are present, move the person immediately to fresh air, investigate the cause, and seek medical attention. For additional information about preventing CO poisoning, visit The US Coast Guard Boating Safety Division website.



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