Short Wing Piper Club
Editor's CornerAfter reading of several recent Carbon Monoxide accidents recently I bought one of those little plastic stick on indicators to put on the inside window of my Colt figuring that it would warn me of any fumes in the cabin. While flying this summer with my 8 year old daughter Ashley in the right seat she asked "Daddy what's that little black spot for?" After I quickly landed I tried a battery operated CO detector from home to check original indication. Sure enough after about 3-4 minutes the alarm went off. A blown exhaust gasket was the culprit! Not the heater muff as I suspected. The following is an article from AVWeb about these detectors which I thought interesting.
While I suppose these chemical spot detectors are better than nothing, they leave a great deal to be desired. For one thing they have a very short useful life, claimed to be 30 to 60 days (and experts tell me that anything more than 30 days is wildly optimistic). Unfortunately, most pilots who use these detectors are very bad about replacing them once a month religiously. C'mon fess up, you know I'm right!
Oh, by the way, if you did replace them once a month, they'd cost you $50 a year!
Furthermore, these chemical spots are extremely vulnerable to contamination from all sorts of aromatic cleaners, solvents, and other chemicals that are routinely used in aircraft maintenance. Read the fine print on these things, and you'll learn that the detectors will be inactivated and damaged by the presence of ammonia, chlorine, iodine, bromine, and nitrous gases. It doesn't take much, either. One brand of spot detector actually warns that the ammonia produced by the presence of a cat litter box in the home may render the detector unusable! What's worse, there's not necessarily any warning that the detector has been contaminated. The bottom line is that you might easily be flying around with an inoperative detector (because it's too old or contaminated) and not know it. In some ways, that's worse than not having a detector at all.
Finally, the chemical spot detectors are incapable of detecting low levels of CO. If you're lucky, they'll just barely start turning color at 100 PPM, but so slowly and subtly that you'll never notice it. For all practical purposes, you'll get no warning until concentrations rise to the 200 to 400 PPM range (and that assumes a fresh, uncontaminated detector). Even at these levels, it can take so long for the color to change to take place that you could easily become impaired before you notice it. As I said, these things are arguably better than nothing, but not by much.
A better spot: the Quantum Eye
An improved version of the chemical spot detector the Quantum Eye is manufactured by the Quantum Group Inc. in San Diego, Calif. This unit sells for about $10 and claims to have a useful life of 18 months (although my experts tell me that 12 months is more realistic). It has an expiration date printed right on its face to help ensure that it won't be used beyond its time. It also has a color reference wheel printed on its face, making it easier to notice subtle color changes.
The Quantum Eye utilizes a "biomimetic" sensor element, which is essentially an artificially engineered chemical whose affinity to CO is as similar as possible to that of hemoglobin. The idea is that CO binds to this sensor material at approximately the same rate that it binds to hemoglobin, and thus the biomimetic detector will change color even in the presence of fairly low levels of CO if the exposure time is long enough. That's a big improvement over the four-dollar chemical spot detectors that are basically insensitive to low levels of CO.
The Quantum Eye is not without its problems, however. Just as with the cheaper chemical spot detectors, the Quantum Eye is quite vulnerable to exposure to a wide range of aromatic chemicals commonly used around airplanes, such as cleaners and solvents containing alcohol, ammonia or chlorine. Such contaminants have a cumulative effect that progressively degrades detector performance over time. Unfortunately, there's really no-good way to determine the degree of contamination or degradation. The only real solution is to replace the detector regularly, and to try and avoid exposure to aromatics.
Another problem with this type of detector is that it can't distinguish between a short exposure to a high concentration of CO and a long exposure to a low concentration both produce the same color change. To put this into aviation terms, the detector may be able to warn you that you're in trouble (assuming you keep it in your visual scan and notice the color change), but it can't tell you what the concentration of CO is and therefore how much time of useful consciousness you have left. This might be okay in the home environment where you can call 911 and then run out the door but it leaves a lot to be desired in an airplane where running outside is not exactly a viable option.
If you're thinking of buying a chemical spot detector, the Quantum Eye is the only one worth considering, in my opinion. AVWeb 1998
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