CO leak in cabin

[flyboy0681]

My Sensorcon Inspector has been showing CO levels recently where readings were  always zero. During cruise I’m seeing 30 to 50 ppm. Oddly, it goes down to zero when I close the cowl flaps. Sometimes on approach with the flaps open and mixture rich, it can reach 100 ppm.
 

Ideas?

 

[RangerM20]

Check the openings in the wheel wells - they should have a Naugahyde boot (or something similar) and be taped or glued to the skin.

[PT20J]

If the readings suddenly increased something has changed. There is a lot more airflow around the exhaust system when the cowl flaps are open. The safest thing would be to assume it's a leak in the exhaust somewhere until proven otherwise.

[toto]

I wouldn’t fly the plane with 30-50ppm at cruise. I would consider it grounded until someone has fixed something. 

[MikeOH]

OSHA's take on CO exposure limits:

 

[Ragsf15e]

27 minutes ago, toto said:

I wouldn’t fly the plane with 30-50ppm at cruise. I would consider it grounded until someone has fixed something. 

I agree. The current level won’t hurt you but it definitely indicates something isn’t right. Especially since it changed.

Traditionally co comes in through the heater muff so maybe start there (boescope?), but a leak in the engine compartment will bleed through gaps in the firewall as well.  Start at the exhaust riser connections and look over the whole exhaust.

[flyboy0681]

Thanks for the tips guys. I'll have to fly her over to my nearest MSC and have them take a look.

[Hank]

59 minutes ago, flyboy0681 said:

Thanks for the tips guys. I'll have to fly her over to my nearest MSC and have them take a look.

With an assistant, you can ground run the engine and have them wave the Sensorcon unit around and see where it is entering the cabin. This will probably be easier to do if you take out the passenger seat first. Don't think you'll want a passenger crawling around in flight doing this.

[toto]

2 hours ago, flyboy0681 said:

Thanks for the tips guys. I'll have to fly her over to my nearest MSC and have them take a look.

I would really feel better with a mobile mechanic who can visit the plane. You can usually find a mechanic at a neighboring field who will drive out for a nominal fee.

If you’re going to do this flight, which I would recommend against, keep a very careful eye on the CO detector, and consider one of these:

[EricJ]

7 hours ago, Hank said:

With an assistant, you can ground run the engine and have them wave the Sensorcon unit around and see where it is entering the cabin. This will probably be easier to do if you take out the passenger seat first. Don't think you'll want a passenger crawling around in flight doing this.

On a friend's experimental we resorted to a leaf blower and some soapy water (or soapless bubbles, whichever you prefer).   Somebody outside the airplane with the leafblower pointing it at all kinds of suspected leak areas and then looking for bubbles inside.     Basically, small airplanes are seives, especially along the bottom.   We finally decided that if it's zero at cruise or close to it, that's a pretty good outcome.    What it does on the ground, or even approach, isn't nearly as important.

[LANCECASPER]

On 9/13/2024 at 8:45 PM, flyboy0681 said:

My Sensorcon Inspector has been showing CO levels recently where readings were  always zero. During cruise I’m seeing 30 to 50 ppm. Oddly, it goes down to zero when I close the cowl flaps. Sometimes on approach with the flaps open and mixture rich, it can reach 100 ppm.
 

Ideas?

 

Sometimes it's as simple as a few missing screws or camlocs on the belly panel(s).