Carl Hancock is one of the lucky ones: one of the few pilots who have experienced carbon monoxide (CO) poisoning, recognized what was happening, and reacted in time to land safely. Potential tragedy was averted through awareness and a couple of lucky breaks, and Carl learned a few lessons that he’s eager to pass on that every pilot would do well to heed.
Carl’s first lucky break happened before his fateful trip. He had interviewed Dan Bass, a pilot who had passed out from CO and, miraculously, crash-landed with minor, treatable injuries, including a whopping case of CO poisoning. So, Carl was keenly aware of the dangers and knew the signs.
Carl’s own rendezvous with CO began on the ground. He was at a top-rated flight school, getting ready to take up a REMOS GX. The plan was to do maneuvers with an instructor, familiarize himself with the aircraft, and get signed off for solo before beginning to work on his instrument rating. There weren’t enough mounts for both the cameras he wanted to bring and for his digital CO sensor, so he decided to leave his CO sensor behind. “I thought, ‘I know they take good care of their aircraft. It’ll be fine.’”
As Carl and his instructor were running pre-flight checks, he could smell exhaust: the second lucky break was that the REMOS ran on automotive-type gas, not avgas, so the exhaust smell was obvious. But the engine was running, and the REMOS’ gull-wing doors were open, so the exhaust smell wasn’t unexpected. Once they closed the doors, took off, and got to their cruising altitude of 2,500 ft., Carl was too busy dealing with the unfamiliar plane and instruments to pay attention to the fact that the exhaust smell was still there. It wasn’t until 45 minutes later, when he was headed back to the runway for some touch-and-gos, that he realized that he had a headache, still smelled exhaust, and was beginning to feel fuzzy-headed. He told his instructor that he suspected CO problems, and they decided scrub the touch-and-gos and call it a day.
Carl collected his gear and went home, and an hour later, he got an email from the flight instructor, who had immediately begun inspecting the plane for the source of the fumes. He found a loose flange on the exhaust manifold, which had allowed exhaust to escape into the cowling and thus into the plane. The flight school repaired the problem immediately, bringing the story to a happy ending.
Carl feels fortunate for those lucky breaks, but he also approaches CO risks differently now. He says the biggest take-away from his experience is to always, always have a digital CO monitor with you. “Especially when flying an unfamiliar plane, you’re relying on the owner-operator to be sure the plane is safe and air-worthy. And even if the plane has been well-maintained and regularly inspected, as this one was, parts can fail between inspections. Many of these aircraft are being flown multiple times a day, and people may not fly it long enough for something to develop, or it may develop a little further the more it’s flown, and the last person to fly it may be the one who gets CO poisoning. So, you have to protect yourself by never flying without a digital CO sensor.”
Carl says you should also be proactive about managing CO risks in other ways. If you’re flying an unfamiliar plane, ask about the last time it was serviced. If there’s an aircraft that you fly regularly, watch the CO monitor and learn what level of CO is normal in it. (In the Cessna 172 that Carl frequently flies, the normal CO level is 0 ppm, so any deviation from that would be a sign of a developing problem.) Try to avoid breathing fumes on the ground, because ambient fumes, cigarette smoke, and other pollution can bring your carboxyhemoglobin (CO-saturated blood) level to a borderline 10%. Cigar smokers can have up to 15% carboxyhemoglobin from ambient CO plus smoking.
Carl says he will also take warning signs even more seriously in the future. Everyone’s sense of smell and everyone’s reaction to CO is different. Carl was aware of the smell and the headache, and his flight instructor wasn’t. Some pilots who’ve experienced CO poisoning report headaches, confusion, and drowsiness, while others have passed out with no warning at all.
Ultimately, Carl says, the hardest thing is to recognize the problem. First, it’s hard to quantify the risks of CO poisoning. “We have a lot of aircraft that crash, but by the time NTSB gets there, the CO is gone. I’m told that the go-to before digital CO sensors was a little card with a dot that would change from gold to black with CO exposure. But that takes over 45 minutes of exposure to change which can be too late for pilots and passengers, and it changes back within 45 minutes, too. If the NTSB got to a wreck within 45 minutes, they would know from that card that CO was the cause, otherwise they would never know. I tested it myself by putting one of those cards under the exhaust pipe of my vehicle, and it never changed. So, I made some calls and found out that it takes an excessive amount of CO to make these cards change. If I had that amount of CO pumping into the cabin, I’d be dead in 10 minutes.”
The second issue is to recognize CO poisoning when it’s happening, and that’s where a digital CO sensor can save your life. “In pilot training, you’re taught about CO and the signs of hypoxia, but it’s not something you think about again after answering the questions on the test. It doesn’t seem relevant until you or someone you know is impacted by it. I talked to a couple of other pilots whose CO alarm went off, so they landed, and within ½ hour of landing they developed splitting headaches. But had that alarm not gone off, they’d no longer be with us because, at that point, they didn’t feel anything was wrong. And that’s the dual challenge: in a plane, you not only have to recognize the problem, you recognize it while you’re still functional enough get safely back on the ground. A digital sensor can buy you the time to do that. In a car, we could roll the windows down and let in fresh air. In an airplane, we can’t do that, and we can’t just pull over and get out.”