I've used one of the digitals for a long time and they really help
keep an eye on whats going on. It's helped me spot exhaust
problems I would have otherwise missed. Some observations
based on my experience:

* I typically see it in the 20s on the ground .. maybe a tad higher
if I'm positioned such that the exhaust is entering the outside air vent.
In the air seldom more than 10ppm.

* When I was having some trouble with cracked risers I'd see
it in the upper 30s to 40s.. on the ground and in the air. While a
higher reading isn't always alarming on the ground if it stays that
way in the air there's a leak somewhere.

* If it goes up when you turn on the cabin heat have the muffler
checked inside the shroud.

* Sometimes getting the seam between the muffler and risers
to seal can be a challenge. I've found in those instances I'd see
a reading in the teens in the air from it seeping into the cabin
from the engine compartment.

As a comparison .. in the winter I often use a propane construction
heater in the hangar if I have something to do on the plane. When
I do I also keep the CO meter handy. I'll see consistent readings in
the 30s. While I've never had any headaches or anything doing this
after a couple hours my eyes will start to burn a little and I generally
limit this to a couple hours at a time.

These meters when used regularly will really help you spot trends
that are out of the ordinary for your plane that you wouldn't otherwise
catch.



"Stu Gotts" wrote in message
...
On the ground, at 70PPM for 20 minutes you will start to experience a
headache. 30PPM @ 20 minutes should not be a problem unless you're
climbing to ~ 8000 or are a smoker or suffer from some respiratory
malady or are in a constant state of inactivity (a lazy *******) . I
would first look real hard for any openings in your firewall to seal
and from there go to any exhaust compromise. I would then have the
ignition and carburetion systems checked to determine why you're
burning so dirty.

For those who aren't able to think, although 30 ppm at the exhaust
pipe isn't high, that much leak into the cabin indicates a bigger
problem at the dump. And as CO is a byproduct of the incomplete
combustion of a fossil fuel, it indicates something amiss in the
cylinders.

On Thu, 01 Apr 2004 23:31:51 -0600, "O. Sami Saydjari"
wrote:

I purchased a C0 Experts Model 2002 about 1 month ago (it is quite
precise and I am generally pleased with it). When I am climbing out
from take-off, I am experiencing relatively high readings of CO, on the
order of 30 Parts Per Million (PPM). This only lasts about 20 minutes
or so. At cruise, it drops to below 10 PPM (considered normal).

(a) Does anyone else have any hard data about their CO concentration
levels in various phases of flight?

(b) I have read that anything above 10 PPM should be checked by an A&P,
but I have read elsewhere that something like 30PPM for short periods is
not a big deal. Are there any medical-types out there that can weigh in
on this issue?