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  1. #1
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    My research on carbon monoxide detectors thus far

    This info applies to devices sold in the USA. I can't speak for those sold in other countries.

    I'm currently shopping for a carbon monoxide (abbreviation is "CO") detector. My gas furnace is old but still works and, each time the maintenance man services it, he performs a carbon monoxide test and he always says I have zero CO emissions. That's great to hear but, gee, maybe I should get a CO detector of my own, one that runs 24/7, so that it can be the canary in the coal mine, instead of me, if this old furnace starts to go downhill between service appointments. I've been reading up on these detectors and found some points that may be of interest to anyone, and I thought I would share it. I suspect few people here may be interested, but ya never know.

    If you have practical experience with your CO detector, please feel free to weigh in and correct any of what I have read. Your device's brand and model number would be useful to know.

    When CO detectors were first being sold (in the USA) for residential use in the early 1990s, the devices did their job effectively and went off any time they detected CO, even at apparently harmless levels. This caused too many false reports to the Fire Departments and to 911 that something had to be done. Underwriters Laboratories then updated their UL-2034 specification to the standard in use today in the detectors for residential use that you buy at places like Home Depot, so that lower levels are not reported. I've tried to read UL-2034 and got lost in all the graphs and charts but, based on benevolent websites that have done the interpretation, here is how you can expect your residential device to perform:

    1) If your unit has no digital display, it will not issue an alarm until the detected CO level rises to 70 parts-per-million (ppm). That will be your first clue of a CO problem. Alarm is 85 dB. It reminds me of an idiot light in your car: no gauge, just an indicator.

    2) If your unit does have a digital display, if any level between 1 to 29 ppm is detected, the display will only indicate "0". Levels between 30 and 69 ppm may be displayed but no alarm will sound, so unless you visually check each time you walk by the device, you won't know. At 70 ppm, an alarm will sound. Alarm is 85 dB.

    (Hmm... when my maintenance man says I have zero CO emissions, is he using a tool that does not display below 30 ppm? Or 70 ppm? Or higher? I'll have to ask him the next time he drops by.)

    3) The levels at which alarms are sounded under UL-2034 require a period of time to have elapsed, for the level detected:

    At 70 ppm, the unit must alarm within 60-240 minutes. So, it can take a 70 ppm level sustained for up to 4 hours to trigger the alarm.
    At 150 ppm, the unit must alarm within 10-50 minutes.
    At 440 ppm, the unit must alarm within 4-15 minutes.

    Expect +/- margins of error in levels reported. Youtube shows side-by-side tests where one unit reported 78 ppm while another unit showed 70 ppm, while both inside a ziplock bag filled with CO.

    Ok, so somebody decided that 70 ppm is the low threshold of safety to health, to prevent all of those dang false alarms to 911 and the Fire Departments. Seems ok, because you can find online charts like the following that show the higher levels are where the danger is:



    Incidentally, here is a Table showing CO levels in various environments:




    These CO detectors for home use are collectively called "high-level detectors". What I found interesting is that I read on many sites, and on the packages of the devices themselves, that these devices are intended for "healthy young people". That phrase was theirs, not mine. The package from a Kidde device said this:

    Individuals with medical problems may consider using warning devices which provide audible and visual signals for carbon monoxide concentrations under 30 ppm. This device is designed to protect individuals from acute effects of carbon monoxide exposure. It may not fully safeguard individuals with specific medical conditions.
    Old people, young children, pregnant women, etc. are outside the range of "healthy young people". That's good to know, yes? Seems that the manufacturers say this to cover their asses, but I did find much info online about this, too much to succinctly present any of it here. If you have elderly people, small children, sickly people, or pregnant people whom you love, you might find such info meaningful.

    They do make "low level detectors" to handle the levels below 30 or 50 ppm and they will sound the alarm when detecting as low as 5 ppm and they display these low levels. They seem to be of interest to aviators who would need to be aware of any CO infiltration into their small aircraft cabins while they are up in the air. These devices alarm after only 1 minute at a certain level, not 1 hour or 4 hours like the residential devices and thus may be referred to as "real time" detection.

    They also sell "real-time" CO detectors for your automobile, in case you are concerned about CO leakage into your car or for those times you are stuck in high-density traffic for a long time (see Table 2 above). However, these car alarms will not sound at 85 dB so as to prevent from startling you into wrecking your car. One model simply lights a red light at 9 ppm then a series of beeps at 25 ppm.

    These low-level detectors of course will not carry a UL listing but that is not a bad thing because, as I wrote above, a decision was made to revise the UL standard to exclude detection below 70 ppm to prevent over-reporting to 911 and the Fire Departments. Low-level detectors are not meant for mass residential use and thus you will not see them at stores like Home Depot.

    I am not young anymore and also my health can fluctuate. I may get both a portable low-level detector and a high-level detector. What the heck.
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  2. #2
    Senior Member Azure Nomad's Avatar
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    Re: My research on carbon monoxide detectors thus far

    Have both in my opinion because having a layer of redundancy is always a good idea. I personally never liked the 2 in 1 smoke and carbon monoxide detectors. I buy a separate carbon monoxide detector and smoke detector. In fact I avoid the digital displays because the sound from both detectors is the true value IMO. This is because fires and carbon monoxide build up is the most dangerous when it happens over night.

    Sometimes the simplest of designs works the best. But you have to decide what is best with what level of information you want from your detectors. But having several layers of redundancy when it is cheap and effect seems reasonable to me.

  3. #3
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    Re: My research on carbon monoxide detectors thus far

    Quote Originally Posted by Azure Nomad View Post
    I personally never liked the 2 in 1 smoke and carbon monoxide detectors. I buy a separate carbon monoxide detector and smoke detector.
    That's what I would do, buy separate units. I read that the actual sensor(s) for the smoke detection, being naturally technologically different than the sensor for the CO detection, means that these different sensors' (guaranteed) operating lives are different from each other such that the CO detector may need replacing a few years ahead of the smoke detector but, in a combined 2-in-1 unit, there you are having to replace both sensors at the earlier time because you bought a combined unit. Or you don't realize the CO detector portion already crapped out after 3-5 years because you think you can wait 10 years to replace the "smoke detector" portion of your combined unit. Better to buy them as separate units.

    I'm thinking having no digital read-out on a high-level CO detector means you may have to memorize the different alarms of your detector to know when it wakes you up in the middle of the night if it reached the lowest 70 ppm alarm level or had reached a more lethal higher alarm level, unless you bought a unit that talks at you, identifying for you with speech which alarm threshold has been triggered. Otherwise, once it finally goes off, how can you know in your 3am grogginess if it had been silently timing a 70 ppm level for 4 hours or a 150 ppm level for 10 minutes, unless you keep a small chart on your wall next to the unit? I assume the false alarms that these imperfect devices reportedly sometimes experience from ambient influences might trigger falsely at the lowest 70 ppm level such that if you woke up to an alarm that you truly knew was for a higher level then you'd know to get the fuck out of your house instead of just silencing the alarm like you did when it went off all those times when you had simply opened the kitchen oven door. Same with a 2-in-1 unit, either memorize the multiple alarm patterns or get one that speaks which alarm is sounding (gas, CO, or smoke, etc.) and/or has a digital display. In a low-level CO detector, it only makes sense to have a digital display and I don't think I saw any low-level CO detectors for sale without a display.

    Somewhere along the way, manufacturers starting putting "Hush" buttons on the units which allow you to press it to silence the alarm while you figure out what is going on. From what I read, before this owners had to remove the battery to stop the alarm and then keep the battery out for an unknown length of time else their alarm would go right back on once the battery was reinserted. It was claimed that owners would just leave their unit disassembled with battery out, forgetting to reinstall it, thus negating the point of having it, so "Hush" buttons were added.
    The two most important days in your life are the day you were born and the day you find out why. - Mark Twain

    The mass of men lead lives of quiet desperation.
    - Henry David Thoreau

    There are 10 types of people in the world - those who understand binary, and those who don't.

    Suitable for bookmarking: www.fakehatecrimes.org and www.breitbart.com/tag/hate-crime-hoax and register-her.net


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