High CO level detected

[Guest]

My wife got me a CO detector for Christmas. I just took it down to the plane today and I noticed that I was getting dangerously high CO levels on the ground. They started dropping during the run up and disappeared with takeoff and remained at zero throughout the flight. I thought there might be a heater shroud issue, so I turned on the heater and still didn’t get any CO in the cabin.  I had the little window on my the pilot side open along with the door. Perhaps this creates some kind of suction?  Any ideas?

[MikeOH]

What were the actual readings when on the ground.  Depending upon wind, run-up, and if the vent window is open I have seen as high as 25 ppm.  Goes away once I take off.

[larryb]

Tailwind or headwind in the ground? I had this happen one time on the ground with a stiff tailwind.

[Guest]

Taxiing, various headings, tailwind  mostly about 10-15 kts, showed 38ppm.  As soon as I landed and opened the door, the reading went right to 10 ppm. 

[MikeOH]

38 ppm seems a little high, but with a 10-15 kt tailwind I suppose it's possible.  Also, no surprise that you saw 10 ppm when you cracked the door open; that is not uncommon on for me, either.

[larryb]

I would give the exhaust system a good visual looking over. Look for white or tan deposits which indicate leaks. As long as the system looks good I would not worry about what you saw. I have seen similar behavior on the ground with a tailwind.

[exM20K]

34 minutes ago, 1980Mooney said:

BTW - what model?  I don’t see it in your profile.

Right.  What model? This is not unusual in the acclaim, and I’d bet it’s common in the ovation. This is why the factory AC is placarded to be off in taxi (maybe climb, too?) left side exhaust dumps under fuselage, so at rich taxi and climb, CO is commonly elevated. Vents open, a piece of paper blocking the bottom right of the door to inhibit Venturi-induced low cabin pressure keep it down.  Monitor in cruise.  Should be 0-3 in my experience on a tocsin detector.

-dan

[Ragsf15e]

59 minutes ago, Kerrville said:

Taxiing, various headings, tailwind  mostly about 10-15 kts, showed 38ppm.  As soon as I landed and opened the door, the reading went right to 10 ppm. 

So 38ppm definitely isn’t “dangerously high”, but it does seem a little higher than most of us see.  I have seen close to that much on the ground with a quartering right tailwind, and the window probably makes that worse.  The house alarms don’t go off until 50ppm for 8 hours or more, so 38ppm isn’t so bad.  I had an exhaust riser come completely disconnected and was seeing around 40s on the ground and 20s in flight.

I might poke around your exhaust but probably just pay attention to the winds and see if you notice a difference?

[Guest]

Thanks for the good info. and shared experience. It is a 20J. Exhaust system looks good. (Too bad, no excuse to change it out for the power flow. )  Maybe I’m overly sensitive to it. The device alarms at 30 and is quite annoying. I’ll just turn it on in flight next time. 

[0TreeLemur]

That happens to me from time to time depending on winds.  I had my SensorCon CO detector actually start beeping once while on the ground with the engine running.   The exhaust smell was pretty strong.  I had the door cracked and storm window open because it was hot in the cabin.   I heard the beeping through my noise canceling headphones.  Its' pretty loud.

[N201MKTurbo]

A while back the run up area at the home drome was backed up and people were running up on the taxiway. The plane in front of me was doing a run up and my sensorcon started beeping.

[Guest]

Those were the conditions, light tailwind, backed up 30 minute taxi, unprofessional controllers complaining on the frequency, Cessna in front of me doing a runup on the taxiway, and I had both door and window open…

 

However, the indications started on initial taxi, they just didn’t get elevated until the fiasco in the run up area. 

[LANCECASPER]

If your door and window are closed on the ground and you're getting much of a CO reading it's usually your door seal that is letting it in.

When in flight feel around the inside of the door seal and you'll feel where the air coming in. If your seal is still in decent shape you might be able to adjust the seal and re-glue it in those areas. If not, you can put some 1/8 inch weatherstrip material on the cabin part of the opening where the door seal meets. Having a good seal on the door quiets the cabin considerably.

[Z W]

When we redid the carpet we took the time to tape up all the seams and holes around the cabin with some high-quality duct tape, after reading that helps prevent CO intrusion as well as cabin drafts.  There are quite a few seams, gaps, and open holes in the floor.  Our exhaust dumps right under the right hand side of the engine.

Got one of the sensitive CO monitors a couple years ago.  It shows up to 5 PPM on the ground with the door and window closed.  Sometimes up to 12 PPM on the ground with the door/window open in the summer.  Have never seen higher than that on it.

[gabez]

I have an m20K231 and I don't get any CO, in any portion of the flight: taxi, runup, climb, cruse or descent. At some point I was seeing 11PPM while climbing and we found a hole in an air hose. 

for what is worth 

[MikeOH]

13 hours ago, Kerrville said:

... I’ll just turn it on in flight next time. 

@Kerrville

Not sure what model you have but that may not be a good idea.  When first turned on mine goes through a self calibration that takes several minutes; pretty sure whatever the background CO level is becomes the '0' reading.  So, any in-flight CO level will read '0' if you do that

[slowflyin]

Lean aggressively for ground ops and it will drop.   Towing my AC with my gas PowerTow results in readings in the twenties in some winds.  Same with fuel truck.  

[Jim Peace]

19 hours ago, Kerrville said:

My wife got me a CO detector for Christmas. I just took it down to the plane today and I noticed that I was getting dangerously high CO levels on the ground. 

That is normal...you will get high readings depending on if the door is open or closed, winds, plane in front of you etc...what counts is that you are single digit in flight.  I shoot for ZERO and that is what I see about 100% of the time.  Sometimes when the heat is on I may see single digits up to 2 or 3...OSHA says you are allowed I think up to 50 for 8 hours....

[Pinecone]

Yes, OSHA limit is 50 PPM for 8 hours a day, 5 days a week.