Carbon Monoxide Detectors

[John Terefenko]

Speaking of carbon monoxide detectors I have 3 specific questions please.

First question: Is it better to mount a detector low on a wall, high on a wall or on the ceiling or does it not matter. You see many detectors that are plug ins with battery backups and usually the outlets are always low normal outlets.

Second question: Do detectors of any kind have the potential to store or build-up residual CO and then after awhile produce a false alarm. I say build up like if say a car in the garage produces some CO but not enough to set the alarm off but after a few times of this it has built up over time. Or your furnace starts up and ever so small amount of CO is released and the same scenario occurs as above.

Third question: Any brand better than another and any one model better than another. Is a digital readout more beneficial than a non one??

Thanks for the replys.

[Larry Frank]

I like the digital readout because it can alert you to a problem long before an alarm would have gone off. I think they do not go off until they reach about 70 ppm.

A number of years ago, my alarm which always read zero started showing levels of 7-8 ppm. I noticed it happened when the gas furnace came on but only lasted a couple of minutes. I called a couple of furnace people and they said not to worry.

Finally, I got someone out to inspect my furnace. Yes, it did have a crack in the heat exchanger and was shut down immediately.

[roger wiegand]

Height doesn't matter in any practical sense. CO is very slightly lighter than air at 20C (room temp), and heavier than air at freezing temperatures. The differential is not high enough to yield stratification in most situations. Generally they are put high to keep them out of harm's way.

Never heard of any long term effect of low level exposure. It's an electrochemical detector, so contamination is a possibility. CO detectors will report false positives in the presence of many things including:
- hydrogen- acetylene
- dimethyl sulfide
- ethyl alcohol (drinking alcohol)
- ethylene
- hydrogen cyanide
- hydrogen sulfide
- isopropyl alcohol (rubbing alcohol)
- mercaptan (odorant in natural gas/propane)
- methyl alcohol/methanol
- propane
- nitrogen dioxide
- sulfur dioxide

[Doug W Swanson]

It does not matter where the CO detector is mounted. Typically people use the plug in ones because they are convenient. I've got two of those in my house (one on each floor) and a combination smoke/CO detector that's hard wired in with the rest of the smoke detectors.

I would get one with the read out just for the sake of seeing what the CO level is should it ever activate. Obviously CO is bad but if your alarm goes off and the CO level is really low, you may be able to stay in the house for a short period of time until you get the CO problem taken care of (you can also help this by opening the windows to get some ventilation). If the CO level is high, then you want to vacate immediately....

[Rich Riddle]

The Honeywell CO monitor directions indicate not to place the detectors too close to any corner such as where a wall and ceiling meet. This is just a general comment about CO detectors, but they do have a rather short lifespan as compared to a smoke detector. I have to replace them every few years for the alarm system.