It’s a routine flight, conditions are good, and everything seems fine, until suddenly the pilot begins behaving erratically, reacting slowly, making mistakes. What’s happening? Carbon monoxide (CO) has taken over this pilot’s brain. And it could happen to anyone. This odorless, invisible gas causes more crashes and fatalities than we can know, because by the time investigators arrive, the gaseous killer has often left the scene of the crime.
The National Transportation Safety Board (NTSB) identified 31 accidents between 1982 and 2020 attributed to carbon monoxide (CO) poisoning, and the Federal Aviation Administration (FAA) found that from 1967 to 1993, 360 victims of aircraft crashes had impaired abilities due to carbon monoxide exposure. As long as aircraft have combustion engines, we can’t eliminate CO risks from aviation, but you can take steps to protect yourself from exposure, and you can learn the signs of CO poisoning and what to do if you suspect a problem. Here are some of the things you need to know.
CO is a by-product of the incomplete combustion of carbon-based materials such as aviation fuel. When you breathe in CO, it binds with the hemoglobin in your blood, replacing the oxygen that the hemoglobin should be carrying to your brain and body. This causes oxygen deprivation, also called hypoxia. The higher the altitude, the faster CO enters your bloodstream. If you get enough CO in your blood, as little as 10%, it begins to affect your cognitive abilities, your vision, and other body functions. Over 50%, and it can cause permanent organ damage and death.
You can have a significant amount of CO in your blood just from environmental factors such as exhaust fumes, other pollution, and cigarette smoke, so even moderate exposure within an aircraft can push your level over 10%. And because CO is 240x better than oxygen at binding with hemoglobin, it leaves your body very slowly. So, a low level of exposure over a long time can be just as bad as a short, high level of exposure. Plus, it can take days to recover from even moderate levels in your blood.
Preventing CO in Aircraft
The most common source of CO poisoning in light aircraft is heating, when air flowing over the manifold picks up exhaust fumes. If you’re flying your own aircraft, you can protect yourself through regular maintenance and inspection, looking for cracks in the manifold, poor seals, and with anything else that could let fumes escape. The older the aircraft, the higher the risk of CO poisoning. The FAA has also found a correlation between the age of mufflers and CO-related accidents, so make sure your mufflers are replaced every 1,000 flight hours or more often. When you’re flying, also be aware of exhaust smells or any other unusual odors.
It’s also worth having a CO detector with you, ideally one that alerts you with noise or , preferably, audible voice alerts, since your brain may not be functioning at 100% if you’ve been exposed to CO. The FAA doesn’t require these detectors, but the NTSB has been recommending them in GA aircraft with closed cabins and forward-mounted engines since 2004.
Knowing the Signs
Regardless of how well an aircraft is maintained, problems can sneak up on us, and many pilots rent planes or fly planes belonging to others. So, you need to be aware and know how to spot CO poisoning before it becomes fatal. It comes on quickly, and by the time you and/or your passengers are experiencing symptoms, you’ve already passed the 10% mark and the situation is serious. Also be aware that CO poisoning affects each person differently, and smaller people (such as children) are even more susceptible.
The first sign of CO poisoning is generally a slight headache. From there, the headache worsens, and the next symptoms can include shortness of breath, a racing pulse, blurred vision, dilated pupils, drowsiness, and confusion. The lips can also turn cherry (bluish) red, on their way to turning blue from oxygen deprivation. If the CO exposure continues, the hypoxia can lead to vomiting, convulsions, unconsciousness, coma, and death.
Reacting in Time
By the time there are symptoms of CO poisoning, you’ve passed the 10% mark and every minute of exposure will make the situation worse. It’s critical to get fresh air and get safely back on the ground. The first things to do are to turn off the heater and increase cabin ventilation using air vents and windows, if possible, to flush out the bad air. If you have supplemental oxygen on board, use it. Reduce altitude to slow entry of CO into the bloodstream, and notify ATC, so that they can guide you safely down and get other aircraft out of the way.
The most important thing is to get on the ground and out of the aircraft as quickly and safely as possible, then seek medical attention. Again, CO can linger in your blood and damage your body even after the exposure stops.
The Invisible Menace
Carbon monoxide is always lurking, it will take over your brain, and it’s a really bad co-pilot. Pilots who’ve had CO poisoning and lived to tell the tale say they struggled to see or understand the instruments, or can’t even remember landing. So do your best to keep this invisible menace out of your plane. To protect yourself and your passengers, conduct your pre-flight check with CO hazards in mind. Be alert for signs of CO poisoning, keeping in mind that each person will be affected differently. Have a quality, working CO detector to alert you loud and clear if there’s a problem. And if you don’t feel 100% for any reason, get safely back on the ground.