Carbon Monoxide Poisoning

Carbon monoxide (CO) can harm and even kill you inside or outside your boat!

Did you also know:
  • CO symptoms are similar to seasickness or alcohol intoxication.
  • CO can affect you whether you’re underway, moored, or anchored.
  • You cannot see, smell, or taste CO.
  • CO can make you sick in seconds. In high enough concentrations, even a few breaths can be fatal.
  • Most important of all, did you know carbon monoxide poisonings are preventable. Every boater should be aware of the risks associated with carbon monoxide – what it is; where it may accumulate; and the symptoms of CO poisoning. To protect yourself, your passengers, and those around you, learn all you can about CO.

danger signReview NIOSH Engineering Reports on Carbon Monoxide.

Review The Center for Disease Control’s NIOSH information page on Carbon Monoxide

Dangers of Carbon Monoxide

The must-know facts about carbon monoxide. If you don’t recognize the symptoms of CO poisoning, you may not receive the medical attention you need.

What is Carbon Monoxide?

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas. It is produced when a carbon-based fuel-such as gasoline, propane, charcoal, or oil-burns. Sources on your boat may include engines, gas generators, cooking ranges, and space and water heaters.

Why is it so dangerous?

Carbon monoxide (CO) enters your bloodstream through the lungs, blocking the oxygen your body needs. Prolonged exposure to low concentrations or very quick exposure to high concentrations can kill you.

Early symptoms of CO poisoning include irritated eyes, headache, nausea, weakness, and dizziness. They are often confused with seasickness or intoxication, so those affected may not receive the medical attention they need.

Altitude, certain health-related problems, and age will increase the effects of CO. Persons who smoke or are exposed to high concentrations of cigarette smoke, consume alcohol, or have lung disorders or heart problems are particularly susceptible to an increase in the effects from CO. However, anyone can be affected. Another factor to consider is that physical exertion accelerates the rate at which the blood absorbs CO.

Emergency Treatment for CO Poisoning

CO poisoning or toxicity is a life-threatening emergency that requires immediate action. The following is a list of things that should be done if CO poisoning is suspected. Proceed with caution. The victim may be in an area of high CO concentration, which means you or others could in danger from exposure to CO.

  • Evaluate the situation and ventilate the area if possible.
  • Evacuate the area and move affected person(s) to a fresh air environment.
  • Observe the victim(s).
  • Administer oxygen, if available.
  • Contact medical help. If the victim is not breathing, perform rescue breathing or approved cardiopulmonary resuscitation (CPR), as appropriate, until medical help arrives. Prompt action can mean the difference between life and death.
  • Shut off potential sources of CO, if possible. Correct ventilation problems and/or repair exhaust problems as appropriate. Investigate the source of CO and take corrective action, such as evacuating and ventilating the area or shutting off the source of the CO, while at the same time evacuating and ventilating the area.

Where CO May Accumulate

You’re not just at risk inside a boat. Knowing all the possible places where CO may accumulate could save your life.

How to Protect Others & Yourself

CO poisoning is preventable. Here are specific steps you can take to help prevent carbon monoxide from harming you, your passengers, or fellow boaters.

Helpful Checklists and Maintenance Tips

A checklist for every trip, plus a monthly and annual checklist. They’re easy for you to print and use.


Carbon monoxide can accumulate anywhere in or around your boat.

How can it accumulate?

canvas enclosures Inadequately ventilated canvas enclosures.
Exhaust gas trapped in enclosed places. Exhaust gas trapped in enclosed places.
Blocked exhaust outlets. Blocked exhaust outlets.
Another vessel's exhaust. Another vessel’s exhaust.
"Station wagon effect" or back drafting. “Station wagon effect” or back drafting.
At slow speeds, while idling, or stopped. At slow speeds, while idling, or stopped.

Be aware that CO can remain in or around your boat at dangerous levels even if your engine or the other boat’s engine is no longer running!

How to Protect Others & Yourself

You’re in command of your boating safety. Follow these simple steps to help keep carbon monoxide from poisoning you, your passengers, or others around you.

  • Know where and how CO may accumulate in and around your boat.
  • Maintain fresh air circulation throughout the boat at all times. Run exhaust blowers whenever the generator is operating.
  • Know where your engine and generator exhaust outlets are located and keep everyone away from these areas.
  • Never sit, teak surf, or hang on the back deck or swim platform while the engines are running. Teak surfing is NEVER a safe activity.
  • Never enter areas under swim platforms where exhaust outlets are located unless the area has been properly ventilated.

Although CO can be present without the smell of exhaust fumes, if you smell exhaust fumes, CO is also present. Take immediate action to dissipate these fumes.

Treat symptoms of seasickness as possible CO poisoning. Get the person into fresh air immediately. Seek medical attention-unless you’re sure it’s not CO.

Install and maintain CO alarms inside your boat. Do not ignore any alarm. Replace alarms as recommended by the alarm manufacturer.

Get a Vessel Safety Check. A VSC is a free bow-to-stern safety examination.

Helpful Checklists

Print and use these checklists, and do not operate your boat without doing the following:

Each Time You Go On a Boat Trip

  1. Make sure you know where CO exhaust outlets are located on your vessel.
  2. Educate all passengers about the symptoms of CO poisoning and where CO may accumulate.
  3. When docked, or rafted with another boat, be aware of exhaust emissions from the other boat.
  4. Confirm that water flows from the exhaust outlet when the engines and generator are started.
  5. Listen for any change in exhaust sound, which could indicate an exhaust component failure.
  6. Test the operation of each CO alarm by pressing the test button.

Once a Month

  1. Make sure all exhaust clamps are in place and secure.
  2. Look for exhaust leaking from exhaust system components. Signs include rust and/or black streaking, water leaks, or corroded or cracked fittings.
  3. Inspect rubber exhaust hoses for burned, cracked, or deteriorated sections. All rubber hoses should be pliable and free of kinks.

Once a Year

Have a qualified marine technician:

  1. Replace exhaust hoses if cracking, charring, or deterioration is found.
  2. Ensure that your engines and generators are properly tuned, and well maintained.
  3. Inspect each water pump impeller and the water pump housing. Replace if worn. Make sure cooling systems are in working condition.
  4. Inspect all metallic exhaust components for cracking, rusting, leaking, or loosening. Make sure they check the cylinder head, exhaust manifold, water injection elbow, and the threaded adapter nipple between the manifold and the elbow.
  5. Clean, inspect, and confirm proper operation of the generator cooling water anti-siphon valve (if equipped).

Downloadable Educational Tools”>Brochures, photos, posters, and other tools to help increase awareness about carbon monoxide and recreational boating.


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