CO Detectors? Let’s Go With Self Help First


In the aviation press, we’re occasionally enthralled by various fads and gadgets often propelled by what readers tell us they’re interested in. Sometimes these emerge from developmental trends in the industry, sometimes the flow goes the other way. That’s certainly the case with carbon monoxide detectors. I’ve done at least three rounds of trials with CO detectors pressed into service from the household and industrial sector. Eventually, the avionics industry responded with panel-mounted detectors, TSO’d no less.

Now the NTSB wants the FAA to require these in GA aircraft. While I restrain myself from knee jerk reactions against all forms of further regulation, I’d view the recommendation more favorably if it were more thoroughly presented by the NTSB. In its recommendation, the agency found 31 accidents between 1982 and 2020 attributed to CO poisoning, 23 of which were fatal. While one fatal accident is one too many, in the remorseless calculus of FAA rules, there’s a tradeoff between money spent and lives saved.

The NTSB opines that the true number of CO-caused accidents is probably higher—I think they’re right. What data they do have represents fewer than one accident a year. Of all the ways we kill ourselves in airplanes, CO-poisoning is somewhat of an exotic outlier. We’ve yet to figure out how keep people from drilling a crater by simply losing control or running out of gas, which happens at least a couple of dozen times a year.

I know, I know … walk and chew gum and multi-task and all the rest of it, but triage is on the other side of that coin. The NTSB’s first recommendation goes back to 2004, when it asked the FAA for rulemaking on detectors. Part of the FAA’s response shows how logically disconnected government agencies sometimes get when sparring with each other. In declining the request, the FAA said it wouldn’t require detectors because CO poisoning is due to exhaust system failures and thus lack of a detector doesn’t constitute an unsafe condition. Huh? That’s like saying deaths are caused by crashes, so lack of seatbelts isn’t an unsafe condition.

In an attempt to find the cure rather than treat the symptom, the NTSB also recommended required replacement intervals for exhaust systems and pressure testing to reveal leaks. The FAA rejected those, too. I think most owners would reject the 1000-hour exhaust replacement cycle the NTSB had in mind. I probably would.

Since it’s the FAA’s job to fill in the blanks here, the NTSB was vague on whether the CO detectors it has in mind should be approved TSO models. In the recommendation letter, the NTSB mentioned the Non-Required Safety Enhancing Equipment standard used to approve avionics and gadgets in certified airplanes. Of course, another logical disconnect arises if the FAA says you can use NORSEE-approved equipment for … a new required equipment rule. Somewhere, an FAA lawyer is reaching for a bottle of Tylenol.

But hold on, I’m still not morally opposed to the idea of detectors, just a little curious about what kinds of airplanes should have them. The recommendation says detectors should be required for “all enclosed cabin aircraft with reciprocating engines.” OK, would that include my old Cub, whose door is rarely closed? Or an old Champ or T-cart? How about twins with combustion heaters? Sure, these can make CO, but are less likely to and I don’t recall any history of them being implicated in accidents.

This needs to be fleshed out a little more, in my view. For the record, I don’t need a CO detector in the Cub. There’s no room for it. I don’t want it. But you might need one and might should have one. You decide.

In the meantime, the NTSB recommends that AOPA and EAA alert their members to the hazards of CO in the cockpit. Yeah, well, we’re all doing that semi-regularly. I have been heard to utter the words “another &^%%*& CO article?” once or twice. We call topics like this “evergreen.” Here’s Exhibit A, Exhibit B and Exhibit C. If you don’t know this hazard by now, will you ever? Some rulemaking hovers on the fine dividing line between must-have and, hey, have you heard of self-help?

Not to be blasé about safety issues, but as for requiring CO detectors. Meh. I’ll get back to you on that.

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  1. The accident rates are at historic lows. They are going to try and justify refitting the entire GA fleet based on 1/2 of 1 fatality per year? That is nuts.

    Let pilots decide. If you want added protection, buy it.

  2. These dueling Government agencies sure do a great job of spending MY (our) money! This is nothing more than another ridiculous knee jerk reaction fix looking for a rare problem … kinda like the ELT issues. THERE — especially now with EPIRBS and ADS-B — why do we even need ELTs any longer?

    For grins, I went to the Spruce pages to look at their offerings for CO detectors and to read the attendant comments. Looks to me as if some of the descriptions allow installations under NORSEE while others are just non-certificated items that sorta work and would just be installed. I did read comments where some units had to go back to the manufacturer for calibration every now and again and for battery replacement. So … from MY perspective … while I’m not adverse to adding a cheap colored dot CO detector for $4, I DO see problems. It’ll become the same as the ELT discussions you’ve had here. False alarms, failure to detect (liability?), cost and etc. The simple stick on detector ought to be all that IS required every annual with more sophisticated and costly units installed at the owner’s additional discretion. I would be absolutely against any required replacement of exhaust systems because they’d likely require R&R of every part of it which is ridiculous.

    Properly maintained and inspected equipment lasts a lot longer than that. I just R&R’ed the muffler on my 172 that I last R&R’ed 30 years ago. I COULD have had a minor crack repaired but chose not to. On exotic airplanes, exhaust equipment is very costly.

    • I won’t advocate for the requirement of CO detectors in the cockpit, but I can say from experience that the TSO detectors we have had in my club planes for at least a decade have never given us false alarms.

      We *have* gotten alerts from time to time while on the ground or during in-flight maneuvering (like slow flight), and they have all been confirmed as true alerts that were due to airflow around the cockpit and exhaust, allowing some exhaust fumes to enter the cabin. Usually changing the aircraft heading (and/or increasing airspeed to recover from slow flight) and opening the cabin window for a bit clears the alert. One of those cheap “dot” detectors would have been completely useless in those cases, not the least of which is because you have to actively look at the detector to see if it has changed color.

      We do have to send these detectors out for IRAN every 5-7 years, but particularly in a club, it is entirely worth the cost (which isn’t even that expensive compared to all other things aviation, even for a private owner). But I would hate to see such devices mandated, because it will almost certainly mean expenses will go up.

  3. The cost benefit analysis is always a challenge for the regulator. The perineal problem is the government tendency to make better the enemy of good enough.

    I have always had the inexpensive yellow dot detector in my Grumman AA1.
    Last fall when it starting to get cold I pulled the heater knob and got the black dot of shame. A full pressure test of the exhaust shows no leaks, the problem was the little flap in the firewall heat on/off box.

    Personally I think there are cheap and proven detectors. Mandating them meets the cost benefit analysis in my view.

  4. Like every issue the bureaucrats play hacky sack with this also will go from recommendation to violation. I’ve flown a lot of hours in Alaska with the defrost/heat on high. The NTSB statistics show of a couple dozen accidents but, there’s more to this story. Many pilots of the north know all about CO poisoning and that it doesn’t always lead to an accident. Quite often it just makes you nauseous and tired. Over time CO accumulates in your cardiovascular/respiratory system and can lead to other more serious health issues.

    Each corner of the country offer a different level of exposure to CO and need the appropriate attention. Alaska aviation should inspect and regularly maintain exhaust systems all year around. Aircraft that don’t fly but a couple times a year in temperatures below 60 F (15 C) can probably check the exhaust once a year during the Annual. Just like they removed the word ‘gullible’ from the dictionary so did they remove ‘Common Sense’. Guess that’s why ‘Big Brother’ has to change people’s diapers and create another regulation ??

  5. I’ve got the portable Sensorcon AV8 units (About $130 ea) in both of my airplanes. They have an electronic numerical read out and are extremely informative. I think these recently came in in AV8 style and are regularly used in industrial settings. We use them in our shop during heating season. You can clip them to your person and they’ll vibrate at about 40 ppm …. Yesterday on climb out in my Cirrus with the vent speed set to “off” we had 6 to 7 PPM registered…. turned the vent on and went to zero very quickly. On cold days I’ve taken my to my R44 training and I can tell you exactly what PPM number triggers the Robinson onboard CO warning light. I don’t have any fancy mounting for my units yet, but I won’t fly without them. I’ll admit I’m not a fan of the “back dot sensor” but I really like this Sensorcon unit. In retrospect I don’t really need the vibrating option because I’m able to place my units where I can occasionally glance at the numerical read out and that is my preference.

  6. We all seem to be in agreement that any mandate of this sort requires a lot more work before it can make any sense – liability issues being one example.

    BUT … can we please also agree to stay away from those stick-on dots. They’re utterly useless and actually dangerous in the sense that they can trigger a false sense of security. They’re not an alarm of any sort – they don’t make a noise. So you’d have to actively look at them on a regular basis, like building them into your FREDA scan, in order to get any sort of indication that something might be wrong. I’ve seen them in charter planes a lot and most of the time, they were expired. So now they have to be part of your pre-takeoff cabin check and you had better have a replacement on hand.

    And finally, if you want to get an idea of how CO poisoning can creep up on you gradually, impairing your own ability to identify it as it progresses, find “Dan Bass CO poisoning” on YouTube. That one is the most compelling case for detectors yet, in my view, because it shows how even a CO-aware pilot can make all the wrong decisions, partially because of the CO in the first place. But they’d have to be of a kind that actually gets your attention and gets you to do the right thing.

    • Thank you, TR. I have railed against the little dot detectors for a long time. Having done some industrial hygiene work in my job, I am familiar with the effects carbon monoxide has on the body, and how difficult it is to remove CO from your system once exposed. The little dot indicators, as you said, have no alarm function so you have to keep looking at them, which you will certainly stop doing as CO builds up. Plus, the color change requires a chemical reaction that will not respond fast enough if the CO level spikes rapidly. As I wrote in a previous commentary on the NTSB CO issue, all of the three standards agencies have a maximum or ceiling level for CO of about 200 ppm, regardless of the time of exposure. Exceed that limit for even 15 minutes and you are in need of immediate fresh air ventilation. Having a personal detector that alarms around 40-50 ppm with either vibration or an audible alarm gives you time to react and investigate, or even land. I carry one of the portable units, and feel that is certainly sufficient for non-commercial aviation use. Plus, it gives a rental pilot the ability to have a known, reliable detector with him/her in what ever airplane they may be using. The odds of exposure may be small, but the potential consequences can be fatal, so you decide. Spending $150 dollars for a device that lasts 7-10 years is peanuts compared to even a new iPad every few years. My personal opinion is that the FAA should recommend all pilots have one but avoid any kind of formal requirement. As Paul says, the FAA has bigger fish to fry.

  7. Seems common sense, if convoluted. Haven’t those tacky color changing CO/CO2 dots have been on aircraft panels since as long as I’ve been involved in aviation (60’s).

    After all, in researching new glass panel gear I’ve found that a CO2 sensor/alarm is increasingly mentioned in the lit as standard.

    Death does not have to be the only gauge of “need.” Flying, in particular, is a game of piled-on contributory causes, carbon poisoning among them.

    Even a touch of CO/CO2 had a profound effect on night vision & altitude tolerance (hypoxia is nothing more than the thinning out of oxygen in the blood, whether by reduced atmospheric pressure at altitude or crowding out by CO2 & carbon monoxide or both.)

    The Military has known the mission imparement effects of CO/CO2 since the days alert pilots chain-smoking cigarettes in the ready room.

  8. I have always believed in CO detectors and bought my first modern, portable detector back when the price dropped below $200, which I velcroed to the top of the panel where I could see the warning lights.

    One morning 5 or 6 years ago I went out to fly and during runup the detector went off big time, so I diverted to the shop where something, I forget what now, was found to be loose and quickly fixed.

    Since this “flight” did not result in a smoking crater, though without the CO detector it well could have, this incident does not appear in any database.

    With detectors now below $100 I think it is foolhardy not to have one in a closed cabin airplane.

    As for the FAA making it a requirement, the issue will be can the FAA use common sense or will the FAA come up with draconian requirements that result in a specification that requires many hundreds, if not thousands, of dollars to meet for what should be a $99 piece of equipment.

    • That is my thought as well. Currently, it will be in the hundreds of dollars if a certified model is required. Now if the increased volume significantly lowers the prices, great, but I don’t imagine prices would come down that much.

      For myself, I also like the idea of having a CO detector. A while back, I was noticing in certain flight regimes I would detect some exhaust odor, so I went and bought a relatively inexpensive battery powered detector with a digital readout, intended for home installation. Sure enough, while the levels did not reach the somewhat high alarm threshold, they were higher than I wanted in my cockpit. Like another poster though, not a problem with the exhaust. In fact turning cabin heat on or opening a vent fixed the problem.

      Turned out the hole through which the elevator pushrod protruded at the very back, bottom of the fuselage with the lower pressure typical of an unpressurized cabin was just the wrong combination. I came up with a seal for this hole (it is a homebuilt aircraft), and my cheap, consumer CO detector told me I had fixed the problem.

  9. The NTSB recommendation shows quite a bit of lack of understanding of CO poisoning in piston aircraft, among other things assuming that the heater needs to be on, or that CO poisoning happens only from broken or cracked exhaust systems. Neither are true.

    CO poisoning can and does happen from airframe leaks, sometimes even coming in from the tail! In fact CO poisoning can even happen in open cockpit airplanes: it is all about where the slipstream is taking that exhaust.

    Personally I use a Tocsin brand portable detector. Leaving it behind one night when I was in a hurry nearly cost my wife and I our lives. The advantage of a portable device is it can be moved from airplane to airplane and placed at different spots in the airplane. IMO what really counts is the CO level where people are breathing the air, which is not necessarily reflected by a panel mount device.

    I don’t care for mandates, but I also think that if you can’t afford $170 for something that can save you and your passengers lives you probably can’t afford to fly, especially considering all the crap pilots tend to spend their money on.

    A couple of days ago I delivered an airplane to it’s new owner and got a ride back in his buddy’s low wing piper, a retired airline pilot’s pampered toy with a lot of new expensive toy’s in the panel. Someone else loaded my bags and I decided not to make a fuss about getting my CO detector as we were on a time table (you would think I would learn!) That night I had a terrible headache, was exhausted and went to bed way early. Turns out the lady in the back seat got a horrible headache too. I shoulda insisted on my CO detector.

    And yeah, those little dots are useless.

  10. I’m not a person to shout “Government Overreach” at things like masking and vaccinations but this kind of knee jerk action is dumb. What I REALLY have a problem with right now is that I can no longer fly model airplanes. They don’t exist any more! Anything without a pilot is a DRONE and needs special licensing and transponders etc. So, because some idiot flew a drone too close to an airport (in London) the FAA saw fit to kill a hobby for a lot of us. GRRR!

  11. I have two (2) portable CO detectors that I carry in my flight bag. The older one alerted several years ago while I was flying at minimum controllable airspeed (high angle of attack) in a Citabria with the doors open on a beautiful spring day. The heater was NOT on. 🙂 That unit cost about $80 when I bought it in 2008. It can’t be recalibrated, but Aircraft Spruce used to sell cans of compressed CO to test it… an interesting binary test. It is no longer made and is an old friend I just carry around for “show ‘n tell”.

    I have another portable CO detector that can be set to alarm as low as I might be interested. It can be calibrated with the same type of canned CO. It has never alarmed in the cockpit of the C182 and C172 I fly. Because I test the calibration every couple of years I am confident it would alert me of CO contamination. Both units have loud aural alarms, and both have a flashing red light that would be very noticeable at night — In daylight, much less so. The cost of my newer unit was $120. A can of CO I bought online for $15 or so is good for several tests. The cost of testing the unit is $0 because I do it myself with my own 15 minutes of labor.

    The CAP and Part 135 aircraft I used to fly just had the dot ‘alarm’… which is absolutely useless. Kinda like 1 micron toilet paper. The dot is impossible to tead in lo light, and not really noticeable even in full sun light. So I carried a portable unit. The units never alarmed.

    I recently bought and had installed a USB charging unit in my cockpit. Cost (parts & labor) about $550. THAT unit doesn’t require recalibration in an avionics shop (likely cost about $300 — perhaps every year).

    We know from years of experience that the FAA doesn’t approve of portable devices. The cost to install panel mounted CO detectors in just the GA fleet would likely cost well over $126,000,000. Testing and calibration would impose another repetitive annual cost of about $35,000,000 per year.

    To prevent less than .7 CO related accidents annually an arbitrary requirement for an unneeded instrument is unwarranted. It would be MUCH more costeffective for the NTSB to make a mass purchase of a boatload of portable electronic CO detectors and ask the FAA to require pilots to carry one on a keychain with the already required photo ID and FAA issued pilot license [JOKE]. Alternatively, mechanics could just follow exhaust system ICAW at 100 hour and annual inspections to easily and effectively mitigate CO leaks with already required maintenance.

  12. My personal experience with the yellow dot CO Detectors has been pretty positive. The three times I have had one turn black has always been due to an actual failure which has allowed CO in the cabin.

    Mounted on the instrument panel puts it in your scan so I don’t see the need to have an audible warning. Sure there are better more sophisticated detectors and good on the pilots who fit them, but the reality is the majority of the privately owned GA airplanes I see don’t have any detectors fitted

    Mandating, at a minimum, a yellow dot type detector would give those pilots a nudge to equip their airplanes. The cost is negligible, but I believe the benefits are real.

  13. Yes! Let’s go with self help. One solution does not fit all. My 120 is so drafty it might as well have one door open even in winter, so I have been using a yellow dot detector. A list of more mitigators:

    > No muffler, just straight pipes which makes inspections from flange gasket to end of pipe easy
    > Cabin heat (toe heater) pulls heat from one pipe only – again easy to inspect between annuals
    > One window vent can be and always is opened in such a way that it pulls air out of the cabin.
    > Stage lengths longer than 30 minutes are rare. Flying this airplane is for fun, not for work.

    CO detectors costing $XXX and up are appropriate for many airplanes but not for my hobby airplane.

  14. My Sentry has a built-in CO detector and it alerted on a recent flight which was right after extensive firewall forward maintenance. We. notified ATC of the alert, they asked if we were declaring an emergency (we did not) and requested we call them when safely on the ground. My daughter and I landed nearest airport for safety & so we could research what CO level 79 meant in risk/danger terms. Turns out 79 is a relatively low level that “may induce headache and nausea with 2+ hours of exposure, danger at 8 hours exposure”. So we opened the cowl and went looking for a possible issue and found it. No RTV was filling the gap in a new firewall pass-through fitting for wiring. Filled the hole, and continued our flight with no further issues. The Sentry served us well that day. And my recent PPL daughter is a true believer in CO detection in the cockpit.

  15. In addition, all occupants of said aircraft must wear five face masks each, with two parachutes tucked under each arm, a football helmet with glare shield and aviator sun glasses. Then all will be well with the world.