Carbon Monoxide

Carbon monoxide (CO) poisoning is the most common type of fatal air poisoning in many countries. You cannot see, feel, smell or taste carbon monoxide.

What is CO?

Carbon monoxide (CO) is a colourless, odourless gas which is produced by incomplete burning of carbon-based fuels, including gas, oil, wood and coal.  Often dubbed the ‘Silent Killer’, it can kill quickly if inhaled in high concentrations. 

Any fuel burning device that is faulty, incorrectly set up and or flued, poorly ventilated or not properly maintained may generate CO. If such a device is on when boaters are sleeping, the often fatal poisoning will occur gradually during sleep with no warning or chance of waking. It is an ever present risk especially for live aboard boaters, both inland and coastal.

How is CO produced?

Faulty boilers or heating appliances, charcoal barbeques, portable gas stoves, and generators can produce lethal doses of CO, especially within confined spaces such as boats.

The RYA endorses the advice on CO provided to boaters by the Boat Safety Scheme. The Boat Safety Scheme warns that CO build-up in boat cabins can occur with one or a mix of these factors:

• faulty, badly maintained or misused appliances

• exhaust fumes from a boat's engine or generator

• escaped flue gases from solid fuel stoves

• blocked ventilation or short supply of air-fuels need the right amount of oxygen to burn safely

Know the danger signs on your boat

There are signs that you can look out for which indicate incomplete combustion is occurring and may result in the production of CO:

• Burners with yellow or orange rather than blue flames

• Soot or yellow/brown staining around or on appliances or its flue

• Pilot lights that frequently go out

• Appliances that are difficult to light and keep lit

• Increased condensation inside windows

• Smell of exhaust fumes inside the cockpit or cabin

Prevent the build-up of CO on your boat

Any appliance that burns carbon-based fuels should be properly installed and serviced by someone who is competent. They will be able to ensure that there is an adequate air supply to run the appliance and that flues are properly installed where they are fitted.

Exhaust fumes, particularly from petrol engines such as the boat's motor or from a portable generator are a prime source of CO. Do not allow any exhaust fumes in the cabin or accommodation spaces and keep generators well away from cabin openings.

LPG fuelled appliances, solid fuel stoves, and similar items also present a risk. All need correct installation, routine maintenance and the right conditions to support efficient combustion, as toxic fumes are caused by poor burning. Ensure your flues are in good condition and check any flue terminals are not damaged or blocked. An adequate supply of oxygen is essential, so never restrict the airflow by blocking cabin vents and air-gaps.

Flue gases from solid fuel stoves, more common to canal boats, can have up to 100 times the concentrations of CO found in gas burners. Smouldering embers and charcoal give off particularly high levels of CO so never bring a cooling barbeque into an enclosed space for any residual warmth.

Install an audible CO alarm that will immediately alert you to any carbon monoxide in your boat.  Install an alarm that is certified to the British Standard as suitable for use when camping and/or in recreational vehicles such as boats and caravans (BS EN50291-2:2010).

Recognise the signs of CO poisoning

When CO enters the body, it replaces the oxygen in the bloodstream and prevents the blood from bringing oxygen to the heart, brain, body tissues, and organs.

The symptoms of CO poisoning are similar to flu or food poisoning, and include headaches, tiredness, nausea and dizziness. The greater the amount of CO the more severe the symptoms will get leading to weakness, loss of balance and memory. Extreme levels may well cause collapse, unconsciousness and death.

Levels that do not kill can cause serious harm to health if breathed in over a long period. In extreme cases paralysis and brain damage can be caused as a result of prolonged exposure to CO. Increasing public understanding of the risks of CO poisoning and taking sensible precautions could dramatically reduce this risk.

Avoid a carbon monoxide incident:

Boat Safety Scheme advice on avoiding a carbon monoxide incident is to:

• Install fuel burning appliances properly

• Maintain appliances and engines routinely

• Use the equipment correctly

• Don't allow engine fumes into the cabin space

• Deal with problems immediately

• Don't allow bodged repairs and maintenance

• Install a CO alarm

• Test the alarm routinely

• Never remove the batteries

• Know the signs of CO poisoning and how to react.

Boaters are urged to follow this advice which will help protect against death or serious injury from the noxious gas.

The Boat Safety Scheme

The Boat Safety Scheme (BSS) is a public safety initiative owned by the Canal & River Trust and the Environment Agency.  Its purpose is to help minimise the risk of boat fires, explosions, or pollution harming visitors to the inland waterways, the waterways' workforce and any other users.

In recognising that it is not possible to eliminate all safety risks, the BSS is employed to help minimise them in a way that balances the responsibilities of the Navigation Authorities and the responsibilities of individual boat owners.

Find out more about the Boat Safety Scheme at

Related documents

10 Carbon Monoxide safety tips

Carbon Monoxide alarms for boats


Boat Safety Scheme