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CO Information


Carbon Monoxide, abbreviated CO, is an odorless, colorless gas. You can not see it or smell it. When inhaled, CO reacts with the oxygen in the blood, and essentially asphyxiates blood cells.

Poorly maintained or misused internal combustion engines can leak carbon monoxide. It follows, then, that people are exposed to the deadly gas when they are exposed to these machines. Severe CO poisoning occurs after prolonged exposure to the gas. Even minimal exposure to the gas can have adverse effects.

Mild effects of CO poisoning include minor eye irritation, dizziness, headaches, fatigue, and inability to think coherently. More extreme symptoms include vomiting, seizures, and collapse. Prolonged exposure can result severe injury or death.

The engine compartment on a boat can present a hostile environment for engine parts. There are three main causes of engine damage that can lead to CO leaks: corrosion, vibration, and wear.

Corrosion, or rusting, comes about from prolonged exposure to exhaust gases and moisture. The dangers of corrosion are present whether you sail on fresh water or salt water, though salt water is more harmful.

In an engine, the up and down motion of pistons produces vibrations which cause fittings to work loose and weak parts to crack and break. Sometimes, metals that have been compromised by vibration look undamaged to the naked eye, so it is important to follow a regular maintenance and replacement schedule.

Also, general wear and tear is inevitable in any engine. We all understand the effect of wear and tear on major engines like automobiles. Boat engines are no different — parts deteriorate and wear out.

We cannot emphasize enough the importance of proper engine maintenance, and regular inspections by experienced and trained engine and generator mechanics. Always follow manufacturer's instructions on proper installation and use of marine engines and generators.

A properly fitted and operating engine can save your life; but merely checking and servicing your engine is not enough.

Even if your engine is in good condition through regular checks and maintenance, CO is still a health hazard on your boat.

There are three main dangers: the "station wagon" effect, obstructions which block exhaust dissipation, and infiltration from a neighbor's exhaust.

Station Wagon Effect
The station wagon effect is related to boat hull design. Boats with tall flying bridges or wheel houses are most at risk. The effect occurs when air is diverted around the flying bridge or wheel house. An area of low pressure is formed behind the flying bridge or wheel house and in below deck cabins. Exhaust from the back of the boat, even when properly vented, can be drawn into this low pressure area, filling the cabins below deck with dangerous CO fumes.

Any breeze blowing from bow to stern can create the problem. So a boat at anchor, bow pointed into the wind, with a generator running can display the station wagon effect.

The immediate solution is to open hatches and portholes so air can flow through the boat.

Sometimes anchoring near a boat house, sea wall, or other large slab-sided objects can block properly vented exhaust fumes from dissipating. The result - your boat could be trapped in a cloud of carbon monoxide gas. It is best to avoid such anchorings altogether, or avoid running generator at such a mooring.

Neighbor's Exhaust
When boats are anchored together in tight quarters exhaust from a neighboring boat can create a CO problem on your own boat. Again, it is best to avoid the situation, but sometimes, at large marinas for instance, it is unavoidable. That is why it is important to make use of a good CO detector.

To help protect against all three of these dangers, Westerbeke recommends installing a reliable CO detector on your boat for those situations where you may be at risk of CO exposure despite your good engine maintenance.

Although there is no general agreement on "safe" levels of CO exposure for humans, there are various published "acceptable concentration levels" according to the U.S. Coast Guard that indicate an occupational day exposure average of 50 ppm (parts per million) would be acceptable for sea level conditions and exposures of 25 ppm for attitudes above 5,000 feet.

  • At an exposure level of 50 ppm for a day, a person's COHb level might reach 10 percent; victims may experience such physical effects as headaches, dizziness and diminished coordination.
  • Levels between 10 and 15% COHb cause nausea.
  • Levels as high as 40% are associated with collapse.
  • Levels over 60% are usually fatal.

Take no chances. If you experience any of these symptoms follow the advice of the American Boat and Yacht Council, "evacuate, ventilate, investigate and take corrective action."