Most small, single engine aircraft are fitted with non audible carbon monoxide detectors that turn black if it is present.

Carbon monoxide can incapacitate in mere seconds (and kill in minutes) depending on the ppm.

If you are cruising at 12,000 feet, that is not enough time to land.

So what should you do if you see a carbon monoxide warning (and begin to feel the effects of it)?

  • 7
    Those dot-style detectors aren't anywhere near as good as an electronic one, you may want to consider having a compact one in your flight bag. If you do use the dot-style ones make sure it's in date as part of your pre-flight check. – GdD Nov 21 at 12:53
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    Just about the only situations where the dot-style detectors could be reasonably expected to serve any useful purpose (whether on aircraft, or anywhere else) would be when there is a slowly-forming leak which doesn't yet pose a danger. Electronic carbon monoxide detectors with alarms and multi-year batteries have gotten so cheap I can't really see much reason not to have one. – supercat Nov 21 at 17:05
  • @supercat UK Consumer magazine "Which?" reported recently that a lot of the electronic CO detectors on sale in the UK don't actually work! (or not well enough to eliminate the risk of slow CO poisoning over several hours). Cheap for a reason? Fire alarms are easy to test. Not so CO detectors. – nigel222 Nov 22 at 10:47
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    @nigel222 Do you have a source for that? Because I've manually tested mine, which only cost about 7 euros and it works fine (tested with a cigarette). – Cloud Nov 22 at 11:04
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    which.co.uk/news/2018/06/… and more behind the paywall. – nigel222 Nov 22 at 11:37
up vote 36 down vote accepted

The first thing you're going to want to do is get fresh air into the cabin, by ensuring the vents/windows are open. This will dilute the amount of CO in the cabin and stop your symptoms getting worse - allowing you to land as soon as practical.

There is also some good information online which contains further advice:

  • Turn the cabin heat fully off.
  • Select maximum rate of fresh air ventilation to the cabin.
  • Open windows if the environment, flight profile and operating manual permit.
  • Consider using supplemental oxygen if available and if doing so would not introduce another safety or fire hazard.
  • Land as soon as possible/practicable.
  • Inform Air Traffic Control of your concerns and intentions.
  • Select a leaner fuel mixture if possible.
  • After landing seek medical attention as soon as possible.
  • Before continuing the flight, have the aircraft inspected by a certified mechanic

If you're wondering about the first point, the reason is that the cabin heat is the primary way CO enters the cabin of light aircraft.

Typically most piston powered aircraft obtain their cabin heating by directing fresh (ram) air over the engine muffler (silencer). If there are any cracks, holes or poorly fitting components in the exhaust system, then CO-rich exhaust gases can enter the cabin. Engine exhaust may also enter the cabin through inadequately sealed firewalls and wheel wells etc.

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    If you get symptoms don't trust that they will go away quickly. With fresh air ventilation CO has a 4-6 hour half life in the blood. It binds very strongly with hemoglobin, so it takes a long time to get rid of it – TomMcW Nov 21 at 20:04
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    Also note, that CO2 is heavier than the air and CO is lighter. CO2 tends to concentrate down and CO tends to concentrate at the top. Strong CO-hemoglobin bond - stronger than O-hem and much stronger than CO2-hem, is the killing feature here - it prevents oxygen to be absorbed in the blood. Get rid of the air around the head ASAP. – Crowley Nov 21 at 20:28
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    @Crowley I don't believe that the stratification of CO and air is significant with the natural air currents you get in an airplane. In fact, it's not significant with the currents in your house, which is why there's no preferred height for CO detectors. – user71659 Nov 21 at 22:46
  • @TomMcW Good point. The point of circulating fresh air is to not make the symptoms worse which will hopefully allow you to land. I'll reword that part of the answer. – Jamiec Nov 22 at 8:24
  • @Crowley Oxygen is also lighter than CO2. Do you expect there to be significantly less oxygen near the floor? – Sneftel Nov 22 at 9:39

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