Carbon Monoxide in my cockpit!!!

Flying off my time in my RV9A. Having trouble with carbon monoxide levels.

Seem to run as high as 40 ppm without any cockpit ventilation opened up. When the vents are open it drops considerably - to zero usually.

Two questions:
1) is there a CO level that is considered acceptable
2) how can I find the source of the exhaust leak that must be producing the CO?
(I have visually inspected the exhaust system - vetterman with mufflers- and it appears intact.

Thanks

dwilson said:

Flying off my time in my RV9A. Having trouble with carbon monoxide levels.

Seem to run as high as 40 ppm without any cockpit ventilation opened up. When the vents are open it drops considerably - to zero usually.

Two questions:
1) is there a CO level that is considered acceptable
2) how can I find the source of the exhaust leak that must be producing the CO?
(I have visually inspected the exhaust system - vetterman with mufflers- and it appears intact.

Thanks

Duane

N32LK flying!!!

Click to expand...

here's some info:
CO EXPOSURE LIMITS - Carbon monoxide exposure limits PEL and TLV set by OSHA and NIOSH

To prevent these effects, OSHA has established a PEL of 50 ppm for an 8-hr exposure, identical to the TLV. NIOSH, on the other hand, has decided to be more conservative and recommends a standard of 35 ppm.

All of these concentrations refer to exposures with durations of 8 hr/day, 40 hr/week for a working lifetime and all are attempts to establish a "no effect" level.

http://www.inspect-ny.com/hazmat/asgasinf.htm


-mike

A DAR that used to belong to our local EAA chapter did some extensive testing on carbon monoxide in RV cockpits. He found a negative pressure area in the tail cone that pulled exhaust up into the back of the plane and eventually into the passenger area. For both insulation from the cold and to keep the carbon monoxide out he made a bellows or sorts, or a elevator pushrod boot that mounted on one of the rear most bulkheads and sealed to the elevator pushrod. From what I remember he was having good luck with the boot. (His plane was an RV-6)

Best,

I was talking with a local 9A builder...they noticed the same thing when they shortened their exhaust pipe. It used to hang down about 6 inches, they cut it almost flush with the cowl and imediatly noticed the smell of exhaust fumes at low airspeeds. Perhaps its being drawn up into the naca vent?

I replaced the aft most pipes in my exhaust system last year, and thought I'd grab a millionth of a knot by having the exit ends a bit higher than the previous setup that I'd flown 5 years. I positioned the pipes' such that perhaps half the diameter of the pipe was below the cooling air exit portion of the cowl. I had a lot of exhaust smell, and presumably CO, at low airspeeds/high AOA's. I repositioned them such that the entire diameter of the pipe is below the cowl, and no more smell.

Dedicated designed cockpit air exit vent any one?

I am more convinced a small reverse scoop on the belly, at least a foot or two aft of the wing trailing edge station would do wonders for fresh air ventilation and even heating for RV's. The previous thread I wrote the following. I just have not got around to cutting a inch or two inch hole in the belly. I have convinced my self that a dedicated exit air vent would improve heating, ventilation and drafts since the exit air will draw and promote air going in the right place (heater or air-vents).

http://www.vansairforce.com/community/showpost.php?p=65279&postcount=7


As it is there is NO ventilation design what so ever. Sure we have NACA scoops and eye ball vents in the panel but where is the EXIT. What goes in must goes out. Its not a ventilation SYSTEM if there is no controlled designed exit. Right now we hope it gets out past rear baggage bulkhead and out the tail somehow, but the tail cone may not be low pressure. The stagnant air does not promote good flow.

In my car (Acura) there are vents in the tail lights that allows air to flow thru the car, into trunk and out the tail lights. From the CFD pressure plots (computational fluid dynamics) of a RV-6A years ago in the EAA magazine, the best place is belly past the trailing edge. I think the idea of Louvers in the inspection panels under the the Horz Stab on the side of the fuselage way aft is not very effective.



Some might think the belly scoop will bleed more exhaust into the cabin? Well with out flight test we will not know, however exhaust wraps around the whole fuselage like a corkscrew. The further back the more diluted it gets. The reason for my guesstimate location is the low pressure area in the belly area aft of the wing. You could go further back. It would just add more duct length. Also the scoop and airflow should produce some negative pressure diff between the cockpit and outside, meaning air should be drawn out.

40 ppm too much

The regulatory numbers for safe exposure, which ever one you go with don't take into consideration the hypoxia associated with elevation. I would shoot for 0.0 ppm. More CO trivia; if you are fully equiped with a pulse Ox finger probe to monitor for hypoxia, it will read CO just like O2 in your blood and show 100% sats even if you have substantial CO poisoning. This thread has me thinking I'll take a meter up with me next flight!

Does anybody else have CO numbers in their cockpit?

Surely there must be others that monitor CO in their cockpits regularly. Are you all seeing 0ppm all the time?

Duane