Carbon monoxide and boats

Carbon monoxide is a toxic gas made by incomplete ignition or burning of carbon-based fuels like petrol, propane, charcoal, wood and oil. You can't smell it, see it or taste it, but it can pose a real threat to the personal safety of those on board your boat.

Carbon monoxide on your boat

Carbon monoxide can accumulate anywhere in and around your boat in all weather conditions and when the boat is moored, anchored or underway. Sources of carbon monoxide on your boat include:

  • engines
  • gas cooking ranges
  • gas space and water heaters.

Boats with partially-enclosed cabins, wheelhouses or passenger accommodation are at higher risk because exhaust fumes (including carbon monoxide) that are discharged overboard can be drawn back into, and accumulate in, these areas.

Carbon monoxide will also collect in areas of the boat near exhaust outlets, such as the swimming platform and during activities like teak surfing, wake surfing and water skiing close to the stern.

Owners and operators of larger boats should also make sure entry into confined spaces such as sealed void spaces, fuel tanks, sullage tanks, battery storage compartments and compartments where harmful gases may be present can, and is, done safely—the Australian/New Zealand Standard 2865 – Confined spaces provides a minimum level for safety compliance in this area. When in doubt, err on the side of safety and exclude entry to these spaces until safe access can be assured.

All boat owners and operators should watch for these situations:

Inadequately ventilated 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. Carbon monoxide from the boat docked next to you can be just as deadly. Another vessel's exhaust. Carbon monoxide from the boat docked next to you can be just as deadly.

'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 carbon monoxide can stay in or around your boat at dangerous levels even if your engine or the other boat's engine is no longer running!

Carbon monoxide alarms

Fitting and maintaining carbon monoxide detectors and alarms is a good way to minimise the risks of carbon monoxide poisoning. Carbon monoxide sensors monitor the level of the gas and make an alarm sound before carbon monoxide levels become hazardous.

It is possible that you may not be experiencing symptoms when you hear the alarm. Do not wait for symptoms and do not ignore your alarm—take appropriate action to ensure the safety of all on board. 

Carbon monoxide poisoning

When carbon monoxide enters your lungs it reacts with blood haemoglobin and reduces the oxygen carrying capacity of the blood. The resulting lack of oxygen leads to tissue damage, long term health problems, permanent brain damage or even death.

High concentrations of carbon monoxide can be fatal in minutes. The cumulative effects mean lower concentrations can also be fatal and cannot be ignored.

Infants, children, persons with pre-existing heart disease and foetuses of pregnant women are more susceptible to carbon monoxide poisoning. Symptoms of carbon monoxide poisoning may be like the symptoms of other illnesses and are easily overlooked.
Early symptoms of carbon monoxide poisoning—such as irritated eyes, headache, nausea, weakness, and dizziness—are often confused with seasickness or heavy drinking.

If carbon monoxide poisoning is suspected, follow these steps:

  • Consider your own safety and act accordingly.
  • Move the victim to fresh air—breathing fresh air will stop the poisoning from getting worse.
  • Carbon monoxide poisoning requires urgent medical treatment and oxygen delivery equipment —if immediate medical assistance is not available, seek medical advice by radio or telephone.
  • Follow first aid procedures until help arrives—be ready to start cardio pulmonary resuscitation (CPR) if necessary.
  • Consult a doctor if anyone experiences even mild symptoms of carbon monoxide poisoning.

Engine and equipment maintenance

Regular maintenance and proper boat operation can reduce the risk of carbon monoxide poisoning. Below are some simple checks for all boat owners and operators:

Before every boating trip

  • Test the operation of each carbon monoxide alarm by pressing the test button.
  • Confirm that exhaust cooling water flows when the engines are started.
  • Listen to changes in exhaust sound—this could indicate an exhaust part failure.
  • Know the sources of carbon monoxide on your boat (such as exhausts and gas appliances).
  • Educate everyone on board about where carbon monoxide may accumulate and the symptoms of carbon monoxide poisoning.
  • When moored alongside or rafted with another boat, be aware of their exhaust emissions.
  • Ensure rain and weather covers are not blocking the free flow of air around the boat.
  • Keep forward facing hatches open to allow fresh air to circulate.

Regular maintenance of your boat

  • Check and maintain your exhaust systems—check mounting clamps are in place and secure; there is no rust, exhaust soot, water leaks, corroded or cracked fittings; rubber hoses are pliable and free of kinks with no burned or cracked sections.
  • Check and maintain the burners on your gas appliances.
  • Check and maintain your carbon monoxide detector—check the battery is installed properly and is in good condition; never remove the battery unless replacing it with a new battery.
  • Have a qualified marine mechanic check your engines every year.
  • Have a qualified gas fitter check your gas installation and appliances every year.

Last updated
23 January 2023