CO2 detectors the "Good The Bad and The Ugly

[skykrawler]

On 10/13/2025 at 5:13 PM, MBDiagMan said:

Great thread!  Recently had someone fly with me that had a CO detector in their headset and it was set off indicating high levels.  I then bought a Sensorcon AV8 and am happy with it.

What no one spoke of in this thread was the levels that they have measured inside the cockpit of their Mooneys and experiences with high levels and how you corrected it would be greatly appreciated.

I was reading 440 ppm through a short flight and it was time for annual. They started trying to find the leak and gave the plane back to me and it’s now reading a little over 800.. They have blocked the heater and they have pressure tested the exhaust and heater system and are unable to explain the high-level.

any experiences that you’ve had with high levels I would love to hear about as we are trying to get to the bottom of this. Thanks for any help you can offer.

It might be worth getting a different device for a second opinion.

[skykrawler]

1 hour ago, Jim Peace said:

Unfortunately we will need legislation to mandate expensive panel mounts due to cheap ass pilots who refuse to smarten up. 
 

No reason to get derogatory.

"A derogatory comment is one that expresses a low opinion, showing a lack of respect by being insulting, demeaning, or disparaging. It can be a word, remark, or comment intended to belittle or diminish a person or thing, with synonyms including insulting, uncomplimentary, and pejorative. Examples include slurs related to race or sex, and insults that suggest someone is stupid or crazy."

We don't need legislation.  That will result in a required CO monitor with a complicated TSO spec that costs $2000 somewhat like ELTs.

 

[Marc_B]

As an aside... @Jpravi8tor can you change the title to "CO" and not CO2?  Every time I see it I get a laugh. 

[Jim Peace]

3 hours ago, skykrawler said:

No reason to get derogatory.

We don't need legislation.  That will result in a required CO monitor with a complicated TSO spec that costs $2000 somewhat like ELTs.

what would you say the percentage of GA piston planes flying today have a great CO detector with live readings displayed in your face?  I am not talking about that scratch and sniff POS....

 

[midlifeflyer]

38 minutes ago, Jim Peace said:

what would you say the percentage of GA piston planes flying today have a great CO detector with live readings displayed in your face?  I am not talking about that scratch and sniff POS....

It's probably tiny.

But not everything requires regulation. And even if you insist on mandating CO detectors, you can do it the way they regulate flashlights, "having at least two size “D” cells, or the equivalent." (we can probably get rid of the "D cells"  language). No panel mount. No TSO. Just something that works.

But the NTSB agrees with you. They have recommended that the FAA mandate CO detectors meeting certain minimum aviation performance standards. They even cited all 31 accidents over a 38 year period that were attributable to monoxide poisoning. Most of those involve fatalities or serious injuries.  So far, I've seen no action on that. 

[Jim Peace]

17 hours ago, midlifeflyer said:

But the NTSB agrees with you. They have recommended that the FAA mandate CO detectors 

I do not want it mandated.  I want pilots to do the right thing and get these portable CO detectors on their own but most will not due to the 100 dollar cost to save their life and their passengers.  I remember when I installed a 406 ELT years ago.  I actually got some backlash from pilots telling me it was crazy to do that being that it was "not required."  I think it was 600 dollars at the time to give me the ability to be found on a map in minutes vs hours or never.....

[MBDiagMan]

22 hours ago, skykrawler said:

It might be worth getting a different device for a second opinion.

Thanks for the suggestion, but it has already confirmed with two separate detectors.  I did that before I confirmed it as an issue.

[MBDiagMan]

11 minutes ago, Jim Peace said:

I do not want it mandated.  I want pilots to do the right thing and get these portable CO detectors on their own but most will not due to the 100 dollar cost to save their life and their passengers.  I remember when I installed a 406 ELT years ago.  I actually got some backlash from pilots telling me it was crazy to do that being that it was "not required."  I think it was 600 dollars at the time to give me the ability to be found on a map in minutes vs hours or never.....

A roll cage is not “required” on my off-road rock crawling Jeep either, but I beefed it up considerably.  Especially since some of my grandkids are with me sometimes.

[midlifeflyer]

25 minutes ago, Jim Peace said:

I do not want it mandated.  I want pilots to do the right thing and get these portable CO detectors on their own but most will not due to the 100 dollar cost to save their life and their passengers.  

Not even that much. 

[Marc_B]

A review of NTSB reports between 1982 and 2020 identified 31 accidents attributed to CO poisoning (see the appendix for a list of these accidents). The data show that 77% of those accidents were fatal and led to 42 fatalities and 4 serious injuries. CO detectors were not found or reported in 30 of those accident reports. Although these accidents can be more prevalent in colder months when pilots are more likely to use aircraft heating systems, accidents related to CO poisoning happen throughout the year; of the 31 accidents between 1982 and 2020, 6 occurred between June and August. The FAA’s service difficulty report (SDR) database also showed at least 45 incidents involving a defect, leak, or failure in engine exhaust systems between 1993 and 2020.

https://www.ntsb.gov/investigations/AccidentReports/Reports/AIR2201.pdf   (same reference as @midlifeflyer above)

The big question is how many could have been prevented with a properly functioning CO detector?  Probably darn near every one.  Its a low volume, but something that we could make a significant impact with I think.

When I upload my engine monitor data to Savvy, it will give me "High CHT" notification even when it was just a CHT probe connection that was erratic, and I get FEVA exhaust valve reports regularly looking at exhaust valve health.  Would be super cool if it would also monitor CO levels and use machine learning to look for trends that this is worsening/changing, or notify if CO levels went over a specific threshold.  Unfortunately this requires integration with engine monitors at current.  HOWEVER, if the CO detector manufacturers would make an inexpensive monitor that has ability to download/store data...then upload or review that...that would pretty slick! 

[Jackk]

On 10/15/2025 at 11:44 AM, Jim Peace said:

what would you say the percentage of GA piston planes flying today have a great CO detector with live readings displayed in your face?  I am not talking about that scratch and sniff POS....

 

 The way most will get their candle snuffed out from their gut, major cause of death is MIs and strokes, by and LARGE the biggest factor there is being FAT

 

Anyone who is above their target BMI I will laugh at if they talk about “safety”

 

 Frankly the Gov goes not keep you safe, rules don’t keep you safe, “safety” is much like the Easter bunny, it’s a made up thing for underdeveloped brains to feel happy about. 
 

 If YOU want to add a CO YOU can add one, but you have zero say what I do, or anyone else does.

 

Heck look at the majority cause of crashes, it’s PILOT error, ie the person just sucks at flying, guess we could have daddy gov say no one with under 3000tt and who doesn’t log at least 50hrs a month should be able to fly,  that would make us “safer” no?

 

[skykrawler]

The accidents cited by the NTSB in this document are hardly insidious.  

https://www.ntsb.gov/Advocacy/safety-alerts/Documents/SA-070.pdf

 

[MBDiagMan]

It seems that this thread has degenerated into a discussion of whether or not to mandate CO detectors. In spite of that fact, I feel that I should continue to post my findings on this problem in an effort to see that someone in the future is helped by it.

we flew it this morning after trying to stop what appeared to be potential CO leaks. A mechanic flew with me with the detector able to move it around and we discovered that the concentration was much higher in the backseat area. What’s on the ground I went to the back of the baggage area and found a gap in the bottom of the very rear baggage compartment panel. They were going to seal up that area and I will fly again Monday. I believe there is a good chance that this is where the problem is.  I believe that it is getting in the tail cone and then forcing past that area at the back of the baggage compartment.
 
I will report back as we learn more. Thanks for your comments and suggestions.

[Ragsf15e]

3 hours ago, MBDiagMan said:

It seems that this thread has degenerated into a discussion of whether or not to mandate CO detectors. In spite of that fact, I feel that I should continue to post my findings on this problem in an effort to see that someone in the future is helped by it.

we flew it this morning after trying to stop what appeared to be potential CO leaks. A mechanic flew with me with the detector able to move it around and we discovered that the concentration was much higher in the backseat area. What’s on the ground I went to the back of the baggage area and found a gap in the bottom of the very rear baggage compartment panel. They were going to seal up that area and I will fly again Monday. I believe there is a good chance that this is where the problem is.  I believe that it is getting in the tail cone and then forcing past that area at the back of the baggage compartment.
 
I will report back as we learn more. Thanks for your comments and suggestions.

There can be a big hole where all the wires come in from near the battery in the tail cone along the left-hand side, Low. That should be sealed up both to prevent carbon monoxide and cold air.

[Skates97]

2 hours ago, Ragsf15e said:

There can be a big hole where all the wires come in from near the battery in the tail cone along the left-hand side, Low. That should be sealed up both to prevent carbon monoxide and cold air.

In addition to that I found that the trim piece around the hat rack opening in my plane was letting in a huge draft which wasn't appreciated by passengers in the winter. There was a gap between that and the plastic shell of the hat rack. I used some duct tape on the back side of the trim piece where it can't be seen to close that gap and the draft was almost eliminated. I didn't have CO issues from there, but something to consider.

[Justin Schmidt]

On 10/14/2025 at 7:00 PM, Jackk said:

Mine are all brand new too, 0 ain’t very real in GA

 

 even my friends 100ish TTSN SR22GTS was like 5-10

I read mostly 0 on taxi. Always 0 in cruise. If i see 50+ on taxi I'll turn around,  back to mechanic because it is out of normal for my plane

[Paul Thomas]

On 10/17/2025 at 6:58 PM, Ragsf15e said:

There can be a big hole where all the wires come in from near the battery in the tail cone along the left-hand side, Low. That should be sealed up both to prevent carbon monoxide and cold air.

What do you seal that with?

[Pinecone]

On 10/14/2025 at 11:40 AM, Jackk said:

0PPM is crazy low with a giant inefficient piston engine, non pressurized cabin, with a exhaust system that’s would be illegal on most cars off a race track

It is not saying 0 PPM in the exhaust, but 0 PPM in the cabin.

And running LOP you can be close to 0 PPM due to near complete combustion of the fuel, as you are running with excess O2 available.

[Ragsf15e]

40 minutes ago, Paul Thomas said:

What do you seal that with?

Excellent question.  I’ve read lots of different solutions.  I think I used some closed cell foam (think pipe insulation) around the wire bundle on my F.  Your mechanic might have different ideas. For me, closing that space changed the temperature a lot, but I wasn’t getting CO in through there.

I haven’t looked there on my K yet to see what is insulating that hole, but the cockpit is definitely warmer at cold OATs than my F was, so I’m sure something is there.

[Paul Thomas]

9 hours ago, Ragsf15e said:

Excellent question.  I’ve read lots of different solutions.  I think I used some closed cell foam (think pipe insulation) around the wire bundle on my F.  Your mechanic might have different ideas. For me, closing that space changed the temperature a lot, but I wasn’t getting CO in through there.

I haven’t looked there on my K yet to see what is insulating that hole, but the cockpit is definitely warmer at cold OATs than my F was, so I’m sure something is there.

Mine looks like some type of putty. It should be a dry area so any seal should do, the lighter the better. I'd think there as to be a cleaner solution than what I have. 

Edited October 20 by Paul Thomas

[MBDiagMan]

Thanks for the replies.

After we flew it on Friday and discovered high levels in the back they sealed things up and said that there is an area , I think around the wire bundle that they want to make a sheet metal cover for, if necessary.  We flew it this morning and found drastically lower CO levels, but still not acceptable.  They have an EXCELLENT sheet metal man that is going to make a shield for the suspect area.

I will continue to report results in an effort to help others in the future.

[Ragsf15e]

3 hours ago, MBDiagMan said:

Thanks for the replies.

After we flew it on Friday and discovered high levels in the back they sealed things up and said that there is an area , I think around the wire bundle that they want to make a sheet metal cover for, if necessary.  We flew it this morning and found drastically lower CO levels, but still not acceptable.  They have an EXCELLENT sheet metal man that is going to make a shield for the suspect area.

I will continue to report results in an effort to help others in the future.

That’s good progress at least.  Depending on your wire bundle there, you might need something pretty flexible between gaps to seal it completely which is how people end up with “putty” or foam or whatever.  It’s an easy place to see for yourself. So maybe when your mechanics are done, take off the battery compartment cover just behind the left wing and look down near the bottom left corner. You should see the wire bundle pass through a bulkhead there.

[Jackk]

On 10/19/2025 at 11:14 AM, Pinecone said:

It is not saying 0 PPM in the exhaust, but 0 PPM in the cabin.

And running LOP you can be close to 0 PPM due to near complete combustion of the fuel, as you are running with excess O2 available.

 Meh, 0PPM I don’t buy in a non pressurized piston, or at least real 0ppm

[MikeOH]

7 hours ago, Jackk said:

 Meh, 0PPM I don’t buy in a non pressurized piston, or at least real 0ppm

You keep harping this.  Frankly, while you are entitled to your OPINION, you are not entitled to deny reality.

My CO sensor performs a self-calibration for zero ppm EVERY time it is turned on.  I.e., even if the sensor is not perfectly accurate at some higher level (e.g. reads 10 ppm when it's really 25 ppm) if it reads zero when in the hanger without the engine running, I can believe that the cabin is a 'real 0ppm' when the engine IS running and the sensor reads zero!

Further, during some run ups, especially when the storm window is open, the sensor reads 10-15 ppm, so that is a FACT which proves the sensor is NOT dead and a zero reading is accurate.

Your view seems to be that you can ignore a non-zero reading in YOUR plane by a false argument that the rest of us 'really' aren't at 0 ppm.  Sorry, that's a BS argument.  You don't want to chase down why your's isn't zero...fine by me. But don't act like the rest of us have non-zero cabin CO when, in fact, we do have zero!

[Jackk]

1 minute ago, MikeOH said:

You keep harping this.  Frankly, while you are entitled to your OPINION, you are not entitled to deny reality.

My CO sensor performs a self-calibration for zero ppm EVERY time it is turned on.  I.e., even if the sensor is not perfectly accurate at some higher level (e.g. reads 10 ppm when it's really 25 ppm) if it reads zero when in the hanger without the engine running, I can believe that the cabin is a 'real 0ppm' when the engine IS running and the sensor reads zero!

Further, during some run ups, especially when the storm window is open, the sensor reads 10-15 ppm, so that is a FACT which proves the sensor is NOT dead and a zero reading is accurate.

Your view seems to be that you can ignore a non-zero reading in YOUR plane by a false argument that the rest of us 'really' aren't at 0 ppm.  Sorry, that's a BS argument.  You don't want to chase down why your's isn't zero...fine by me. But don't act like the rest of us have non-zero cabin CO when, in fact, we do.

 It’s not zero, with a real instrument I promise you it ain’t zero

 

 it’s like new car gauges, they default to less info to not scare Susie