A popular brand of CO monitor..

LAST UPDATED ON 2006-January-23!



Now, Let's Get This Right For Once!

For some bizarre reason people have an annoying tendency to confuse these two gasses.

For those who aren't chemistry gurus, CO is chemical shorthand for carbon monoxide. "Mon" infers "one" as in monotone and monologue. There is a subscript "1" inferred to each letter of the abbreviation. Read CO but think C1O1. This denotes a molecule composed of one atom of carbon and one atom of oxygen.

By contrast, CO2 is chemical shorthand for carbon dioxide. "Di" infers "2" as in dialogue and dichotomy. A carbon dioxide molecule is composed of one atom of carbon and two atoms of oxygen.

Arsonry 101

From a chemist's point of view, any substance that contains carbon is considered to be "organic." Thus, everything from petroleum and coal to the steak you cremated on the bar-bee last weekend are composed of organic compounds. When you burn an organic (carbon bearing) substance in plenty of oxygen, one of the primary results is carbon dioxide. However, if you burn it with insufficient oxygen, not all the carbon has an opportunity to completely combine with oxygen and a significant amount of carbon monoxide is produced.

By a different process, most living organisms (Notice the qualifier. Let's not go there!) also produce carbon dioxide. The breath of humans, for instance, is composed of about 4½% carbon dioxide in spite of the fact that our inhaled air contains less than ½%.

So What's The Big Difference?

Carbon dioxide is colourless, but has a slight odour (smell the gas from a bottle of soda pop next time you open one) and a mildly acidic flavour. CO2 is produced in huge amounts by us as we breath. Our physiology is set up to detect high concentrations of carbon dioxide and we quickly react to it. It is also only mildly toxic and only in relatively high concentrations.

By contrast, not only is carbon monoxide colourless, it's also odourless and tasteless. Thus, it's completely undetectable unless we use some artificial detector. Also unlike CO2, CO has an extremely strong affinity for haemoglobin, the red pigment in our blood that picks up oxygen from our lungs and carries it to all the rest of our body. Haemoglobin that is tied up with CO can't carry oxygen. If we're exposed to even trace amounts of CO in our air our blood preferentially filters it out and combines with it to the exclusion of oxygen. In effect we suffocate.

Now you know. Test on Friday!


We've all read the brochures and are sick until vomiting of reading about tasteless, odourless, yadda, yadda, yadda. In spite of this, a few of us manage to die of CO poisoning every year anyway. The last I heard, CO detectors in motorhomes, fifth wheels and travel trailers have been mandated by law for years. Thus, one would expect that the various manufacturers would have had enough experience to get it right by now. Either the RV industry is terminally retarded or some government agency is meddling again.

During the trip north from Georgetown, Texas our chassis battery went dead on us on two occasions for no apparent good reason. We hadn't left the headlamps on and the battery was one of those types that you cannot open to refill with water so it probably wasn't in need of servicing. Besides, the battery carried a sixty month warrantee but was less than 2½ years old so it shouldn't be dying yet.

Then, one evening, Stan read a posting by someone on one of the Internet's RV forums concerning their battery persistently going dead in a Dolphin. They traced the problem to a CO monitor that was wired to the chassis battery rather than the RV battery.

The problem with that scheme is that there is no way to turn the CO monitor off. All the while your RV is sitting there without either shore power, generator power or the engine running, the CO monitor is draining your chassis battery. Way to go, buffoons!


This not a fault with the various makes and models of CO monitors. They're doing exactly what they were designed to do and probably are doing it quite reliably, too. It's not a CO monitor problem. It's an RV manufacturer problem.


The obvious solution was to rewire the CO monitor so that it draws power from the RV batteries instead. That way, when you hit the disconnect switch as you leave the premises, it turns off with everything else and doesn't do any damage. Stan did this and to date has had no problems with either battery (chassis or RV) going dead in spite of the fact that the Duchess was stored all winter two years in a row. Quite obviously it wasn't the health of the chassis battery that was causing the problem.

"But how will you know if there's a dangerous CO build-up while you're gone?" you ask. Answer: "It doesn't matter when you're gone!" And, when you return and unset the disconnect switch to restore power, the CO monitor reboots and goes whacko in plenty of time for you to escape or solve the problem.

On the Internet mailing lists this subject has been addressed several times. Quite often we find the comment that the carbon monoxide detector draws so little power that it should take a year to drain a healthy battery. This is obviously one of those cases where theory and reality collide. Guess who won!

Several other respondents suggested turning the CO detector off or pulling a fuse so it wouldn't drain the battery in the middle of the night and shut down your furnace. This is so idiotic it's almost (but not quite) unbelievable! Why would anyone in their right mind turn off an alarm during that period when they need it most? I wonder just how many of these fools actually qualified for a Darwin Award!


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Copyright © 2006, Stanley A. Schultz and Marguerite J. Schultz.
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This page was initially created on 2006-January-23.
The last revision occurred on 2006-January-23.