Wintertime and CO levels

[Danb]

It’s now cold in the northeast,and we’re using our heaters. What is acceptable CO readings during taxi and flight.

I noticed my readings were 50+ during taxi and finally went to zero in level flight. Is the higher reading problematic during taxi. I went to Weber and had them check my system for leaks none found.

[N201MKTurbo]

Some say 600 ppm would be the tripping point for climate change. Your engine makes the same amount of carbon dioxide no matter what time of year it is.

I think you were talking about CO...

[Andy95W]

There was a thread 2 days ago that was talking about this.  Someone posted this table:

My CO detector also goes high while taxiing, but goes down to about 2-5 in flight.  One time it read 35 in flight, but even opening windows and vents had no effect on it.  The next flight it was back to normal, so it must have been a detector anomaly.

I think for me, anything over 100 is an emergency, anything over 35 means I'm taking off the cowling to investigate when I get to my destination, 50 while taxiing means I'll shut off the heater, open the vents, and takeoff ASAP.

[Bob_Belville]

Data point Dan, I sometimes see 30-50 on the ground but in flight even with the heater on I see only zero. 

[Danb]

thanks I was concerned with the 50+ reading on the ground

[Mooneymite]

I also get 15-30 during taxi.  Zero in flight.  I normally taxi with the door ajar and have always assumed the propeller wash on the ground caused the higher readings.

[Marauder]

Dan - I see between 8 and 15 on the ground and less than 5 in flight.


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[Skates97]

In the southwest I don't use the heater much... so these numbers are all without heat on, although with the vents open. I see around 10-15 on the ground. On climb out it is random and I have given up trying to chase it down after replacing door seals and checking all kinds of other areas that it could be coming in from. Sometimes I see 30-50 in the initial climb and sometimes it is 5-10. Once in cruise it always drops to 0 and then I will see it coming back up to around 10 on descent and into the pattern.

I did turn on the cabin heat yesterday just to see if it had an affect and it crept up to 2, once the heat was off it went back down to 0 so I will be looking at that with my IA when I do the annual next month. A reading of 1-2 doesn't concern me, but I would like to know where it is coming from and if it is going to get worse. I was able to repeat the results by turning the heat on and off so I know it is related to that.

[skydvrboy]

Like @Skates97, I see around 10-15 on the ground... unless I forget to lean and then I can get up to 50 - 60.  If you're reading 50+ during taxi, check your mix.  I also have readings all over the place during climb, anything from 5-50.  I also always see 0 in cruise.  I don't worry about small leaks that can let some CO get in through the body of the plane, it's leaks in the exhaust or heater that will get you in trouble in a hurry. 

If there is any question, to where the CO is coming from, turn on the heat and move your detector to the heater vent.  If your levels go up, you have a problem, if they go down, you're getting it from somewhere else. Anything in the 50 ppm isn't going to hurt you unless you are on a LONG flight, but it is enough to monitor and see if it keeps going up (Yikes) or starts going down (Whew).

Calling @DanM20C for further comment, as he's our resident CO expert.

[Hank]

Every time I check mine, it's at 0, in the air or on the ground. Need to Velcro it below the quadrant. Even holding it in the heater flow, it reads 0. When I first got it, I did see some numbers as high as 3, with the heater on in my truck immediately after starting on a cold morning. Went to 0 in just a couple of miles.

[carusoam]

Cold engine start-up can be a source of slightly higher CO levels than an already warm engine... dynamics of chemical reactions can be the cause...

I found my CO sensor beeping loudly in my car this week.  Each time I started it the CO would peak for about 30 seconds until falling off...

Of course auto emissions are dependent on catalytic converters getting warmed up too...

While stopped on the ground, and taxiing, we are going to see some CO as the exhaust pipes are at our feet...

One way to minimize the CO would be to warm the engine quicker and leave less fuel to partially burn. Lean to peak or as close to peak as possible.

 

Another thing to look into... environmental issues acceptable to the CO sensor...  Make sure the sensor isn’t needing to warm up for accuracy...

See if @DanM20C has the environmental details handy?

Expect some CO to be a transient effect... for a few minutes until the engine warms... at the run-up everything should be the same as usual... no more, no less...

PP thoughts only, not a CO expert...

Best regards,

-a-

[DanM20C]

  On 11/5/2018 at 5:02 PM, skydvrboy said:

Calling @DanM20C for further comment, as he's our resident CO expert.

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Thanks Mark, but I am no expert. 

I encourage people to use their CO detector (high resolution) as a tool to get to know their particular airplane.  When there are deviations from "normal" you can quickly determine and troubleshoot the problem.

CO during ground ops is common and expected. 

Many report slightly elevated readings during climb and decent too.  It you see this it is worth troubleshooting.

In cruise there should none.

Testing the heating system is as simple as watching for a rise with the heat on, and a drop when off.  this can be done quickly by holding the detector in front of the heat vent. If you get a repeatable rise (even small 5-10ppm) when turning the heat on you know there is a breach in the heating system.  A problem that will most likely get worse over time.  The nice thing with these modern detectors is it allows us to catch problems early.

The above chart the @Andy95W posted above is not conservative enough for me when it comes to aviation, yet the FAA uses it in their literature.  I had one new airplane owner report getting headaches and overall felling unwell after every flight, some less than an hour.  He then purchased a Sensorcon and found an average of 150ppm during cruise.  According to the chart he should have felt nothing.  I think everyone reacts differently.  Andy's 100ppm emergency limit is a good one.

Anthony, I don't have any environmental details handy for the sensorcon.  I'll reach out to them an see if I can get more info.

Cheers,

Dan

[jaylw314]

  On 11/5/2018 at 2:24 PM, Andy95W said:

There was a thread 2 days ago that was talking about this.  Someone posted this table:

My CO detector also goes high while taxiing, but goes down to about 2-5 in flight.  One time it read 35 in flight, but even opening windows and vents had no effect on it.  The next flight it was back to normal, so it must have been a detector anomaly.

I think for me, anything over 100 is an emergency, anything over 35 means I'm taking off the cowling to investigate when I get to my destination, 50 while taxiing means I'll shut off the heater, open the vents, and takeoff ASAP.

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The main concern about that chart is that we are normally exposed to the highest CO levels at startup and taxi, and then we go flying for potentially a few hours at altitude where we have less oxygen.  Since CO exposure will result in prolonged effects (at least 24 hours), I'd think those numbers still might be a little optimistic.

On the other hand, exposure is related to both concentration and duration, and startup and taxi should be brief enough to limit exposure.  I get about 40-60 ppm during taxi.  I think about doing the following, although it's not clear how much they help:

• If you stop, point the plane into the wind.  That way, exhaust will be blown by the wind and prop behind the plane and away from the front air intakes and the window/door.
• If you have the tail intake for the roof, close that!
• If CO increases too high on the ground, CLOSE the vents and windows, and continue to monitor CO.  CO is not coming through the heater, it's coming from outside.  Obviously, buttoning up is an issue on hot days, though
• Lean out the mixture as much as possible on the ground.

[ilovecornfields]

  On 11/6/2018 at 6:04 PM, jaylw314 said:

The main concern about that chart is that we are normally exposed to the highest CO levels at startup and taxi, and then we go flying for potentially a few hours at altitude where we have less oxygen.  Since CO exposure will result in prolonged effects (at least 24 hours), I'd think those numbers still might be a little optimistic.

On the other hand, exposure is related to both concentration and duration, and startup and taxi should be brief enough to limit exposure.  I get about 40-60 ppm during taxi.  I think about doing the following, although it's not clear how much they help:

• If you stop, point the plane into the wind.  That way, exhaust will be blown by the wind and prop behind the plane and away from the front air intakes and the window/door.
• If you have the tail intake for the roof, close that!
• If CO increases too high on the ground, CLOSE the vents and windows, and continue to monitor CO.  CO is not coming through the heater, it's coming from outside.  Obviously, buttoning up is an issue on hot days, though
• Lean out the mixture as much as possible on the ground.

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I think those are great points. Probably worth remembering since CO has a much higher affinity for hemoglobin than O2 so if you get a big exposure on the ground, you’re probably even worse off than you would expect at altitude. I think that chart which I posted assumes sea level conditions. Pulse ox won’t help since very few can differentiate CO from O2 and CO exposure will cause an erroneously high reading for SpO2.

[skydvrboy]

  On 11/6/2018 at 5:23 PM, DanM20C said:

Thanks Mark, but I am no expert. 

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In the land of the blind, the man with one eye is KING!

[jaylw314]

  On 11/6/2018 at 7:47 PM, ilovecornfields said:

I think those are great points. Probably worth remembering since CO has a much higher affinity for hemoglobin than O2 so if you get a big exposure on the ground, you’re probably even worse off than you would expect at altitude. I think that chart which I posted assumes sea level conditions. Pulse ox won’t help since very few can differentiate CO from O2 and CO exposure will cause an erroneously high reading for SpO2.

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Forgot to mention that, that's a biggie!

[exM20K]

  On 11/5/2018 at 12:46 PM, Danb said:

It’s now cold in the northeast,and we’re using our heaters. What is acceptable CO readings during taxi and flight.

I noticed my readings were 50+ during taxi and finally went to zero in level flight. Is the higher reading problematic during taxi. I went to Weber and had them check my system for leaks none found.

Expand  

That is about what I see in the Acclaim, but I don't think it's from the heater.  It is from the exhaust under the cabin.  Acclaim heat is from upper deck, not muffler, and i get the same readings regardless of whether or not the heat is on.

Drops to 0 after level-off.

-de

[Andy95W]

  On 11/6/2018 at 6:04 PM, jaylw314 said:

 

If you stop, point the plane into the wind.  That way, exhaust will be blown by the wind and prop behind the plane and away from the front air intakes and the window/door.

• If you have the tail intake for the roof, close that!
• If CO increases too high on the ground, CLOSE the vents and windows, and continue to monitor CO.  CO is not coming through the heater, it's coming from outside.  Obviously, buttoning up is an issue on hot days, though
• Lean out the mixture as much as possible on the ground.

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Good recommendations for on the ground.

[M016576]

  On 11/5/2018 at 5:51 PM, Hank said:

Every time I check mine, it's at 0, in the air or on the ground. Need to Velcro it below the quadrant. Even holding it in the heater flow, it reads 0. When I first got it, I did see some numbers as high as 3, with the heater on in my truck immediately after starting on a cold morning. Went to 0 in just a couple of miles.

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That sounds good- but it seems like everyone else is seeing some reading other than 0 during start and taxi... might be worth testing the unit in a known CO environment, or running a calibration on the unit- just for piece of mind.

[Hank]

  On 11/7/2018 at 2:43 AM, M016576 said:

That sounds good- but it seems like everyone else is seeing some reading other than 0 during start and taxi... might be worth testing the unit in a known CO environment, or running a calibration on the unit- just for piece of mind.

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No change before / after calibration, but I've not checked during taxi withnthe door open. 

[M016576]

  On 11/7/2018 at 11:00 AM, Hank said:

No change before / after calibration, but I've not checked during taxi withnthe door open. 

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Another option to check it would be to just hold the sensor con near the exhaust pipe of your car- that should probably verify that it’s working.  I’d say near the exhaust pipe of the plane- but that might be a bit irresponsible!

[N201MKTurbo]

One thing nobody is mentioning is exhaust entering through the belly panels and wheel wells. Any gaps or wrinkles in the belly skins can let exhaust into the belly then up behind the upholstery and into the cabin.

Also check your rat socks in the wheel wells. They are actually there to keep exhaust out of the plane not rats.

[Hank]

  On 11/8/2018 at 6:30 AM, M016576 said:

Another option to check it would be to just hold the sensor con near the exhaust pipe of your car- that should probably verify that it’s working.  I’d say near the exhaust pipe of the plane- but that might be a bit irresponsible!

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Sensorcon's literature recommends NOT putting the sensor up to engine exhaust. Mine performed well during calibration using their supplies and systems, I'm not worried that it suddenly doesn't work. Guess the new muffler I out on ~100 hours ago is still in good shape!

[65C_flier]

I ran into @DanM20C at the Mooney tent at Oshkosh last week and he very helpfully calibrated my Sensorcon (by the way thanks Dan!). My CO level has always been around 10-40PPM on the ground and less than 10 in flight, but on the flight out of OSH the Sensorcon triggered the 35PPM alarm a few times (max of low 40s). I assumed it was related to the calibration until the next flight when the same thing happened, but this time my Sentry also triggered (inbuilt CO monitor that interfaces with Foreflight, but no PPM reading). I did some troubleshooting with cabin heat, cowl flaps, etc and there was no clear trend. As soon as I got home I did the trusty shop vac in the exhaust and soap water spray trick. Sure enough 2 of the ball joints have pretty good leaks. Time for some exhaust maintenance and resealing the cabin! Highly recommend carrying a CO monitor and keeping it calibrated.

[gsxrpilot]

My SensorCon is usually at 0 but sometimes I see it as high as 10 while taxiing on the ground. 

On one flight it was reading in the low 50's during a short flight. I landed, took the cowl off and found the oil breather tube disconnected.

I won't fly in a Mooney without shoulder harnesses and won't fly in one without a SensorCon or Guardian CO detector.