PIREP--CO Experts low level carbon monoxide detector

Many of us cold-weather pilots worry about carbon monoxide in the cabin,
especially in winter. After using the "dot-that-changes
color-on-a-piece-of-cardboard" carbon monoxide detectors for the last 9
years, we decided to look at the new battery-operated detectors.

Last year I made a foray into this field by buying a Wal-Mart home model.
It turned out to be too big for use in the plane, and had an alarm threshold
that was set too high. I got the distinct feeling that we would be dead long
before the alarm ever sounded. After tripping over it for a few months, it
migrated into our home -- and we went back to the "dot-on-the-cardboard"
model.

When www.Aeromedix.com started advertising their "CO Experts" low level
monitor, it sounded like just what we were looking for. While it's still
not tiny, it's much smaller than the home model, and it displays carbon
monoxide levels at a MUCH lower level, without sounding a stupid alarm until
the levels become worrisome.

When they offered it on sale for "only" $99, I bought one. We've been
flying behind it now for several weeks of cool-to-cold weather, and here are
our results:

1. Convenience. I briefly considered mounting it to the ceiling with
double-back tape, but I feared it wouldn't stick for long. Thus, I settled
on mounting it just to the left of the pilot's yoke, on the side panel. To
hold it there I simply installed a longer screw in the side upholstery, and
"hung" the unit from the screw. (It has a screw-mount hole on the
backside.) This has proven satisfactory -- it's a nice looking unit, it's
not in the way, and it's clearly visible for both pilot and copilot. It
can also be easily removed in the summer, if desired. (Which we won't do,
for reasons listed below.)
Rating: Fair. (I'd rather it was smaller.)

2. Usability. Controls on the unit -- which runs on a single 9 volt
battery -- consist of a digital LCD readout, and a test/reset button.
Before each flight we push the test button, which sounds an alarm tone and
runs the unit through a diagnostic routine. It's simple, easy, and requires
nothing more than a single push of a single button to assure that it's
working.
Rating: Excellent.

3. Sensitivity. On take off, at high angles of attack, it's not unusual to
smell exhaust in our plane. The 235 is capable of some fairly impressive
climb rates, especially when lightly loaded, and I like to get high as
quickly as possible -- so suffice it to say that we routinely smell exhaust
during the climbout.

I've always wondered how much CO we were getting in the cabin when this
happened, but the "dots-on-the-cardboard" never registered anything.

The CO Expert immediately came to life during climbout, showing a read-out
of from 10 to 17 parts per million. (The FAA minimum is 50, so this is not
alarming.) Once we leveled out, the smell went away, and the CO Expert went
blank. The unit updates every SIX seconds, so it reacts very quickly to
changes, and it appears to be every bit as sensitive as they say it is.
Rating: Good.

4. Results. In cruise flight, we register no CO in the cabin.
Surprisingly, our highest readouts have been observed upon throttling back
to enter the pattern -- with the heater OFF. Levels as high as 34 ppm have
been observed (still well below the FAA threshold of 50 ppm) on downwind in
this flight regime, which surprised us.

Again, the angle of attack is different during slow flight, so the exhaust
is apparently being drawn into the fresh air ducts (perhaps up on the tail,
according the Cherokee Pilots Association) during this stage of flight.

Interestingly, turning the heater on (and thus pressurizing the cabin a bit)
caused CO levels to drop back to zero. Nice to know our heat exchanger is
evidently not cracked!

5. Conclusion. The unit works as advertised, and has given us confidence
that our aircraft is safe. We are confident that the CO monitor will give
us ample warning of high CO levels in the cabin should a heat exchanger
crack, or some other leakage develop.

Since the highest levels of CO have been observed with the heater off, it's
easy to see that carbon monoxide isn't just a cold-weather issue. I think,
however, that you won't see potentially dangerous levels of CO in the cabin
unless you're getting it through a bad heat exchanger, or a scat tubing
leak -- but since the unit takes up so little space we'll probably just
leave it in the plane all the time.

Overall Rating: Excellent. I'd buy it again.

See it at http://makeashorterlink.com/?E3E8243E9
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"