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co detector....

Brad White
Brad White Member Posts: 2,398
a local AHJ on a school boiler replacement project. He wanted the CO detectors about 18 inches off the floor, his thinking that CO was heavier.

My argument was that CO was miscible with and at about the same density as air and in a boiler room would tend to accumulate higher because of convection. (Try as we might and insulate the place, even in winter, those boiler rooms get warm..).

The source of CO starts warmer than ambient by definition and so would make an initial rise with convective currents.

I made the case that breathing height or a tad above would be better (pretty much what the CO detector manufacturer recommended) and that if low-down could be kicked and damaged to the point of being useless.

Also a low detector would finally go off next to the ear of a dosed and fallen trades-person but would not wake them up unfortunately.

The AHJ accepted this.
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

-Ernie White, my Dad


  • re opening an old wound... c0 question...

    Almost condemned this boiler due to insulation panel fell onto burner tubes, thanks god with the burner flames inpindings(sp) the thermocouple and burnt up same ( pre-flame out shut off model), I removed the falled insualtion and cemented the opening, I took customer's c0 detector and relocated same in bolier room for extra safety. I explained the customer the safety and the high risk and the very limited false safety with the c0 detectors ( please read Mark Eatheron's articles regarding same in Contractor magizine)... Her husband said that c0 settled at lower level and I'm doing it wrong by hanging at 'eye' level.. .. So it got me thinking " no way" its the 'lighter' than air, same as the smoke detectors...
    So where should the c0 detectors should be? Upper or lower part of room...?
    Thank you Mark for the thought provoking articles and as well the past....
  • Mark Hunt_3
    Mark Hunt_3 Member Posts: 184

    I told folks to keep the detectors on a dresser or night stand. CO is lighter than air, not by much, but still lighter.

    CO alarms should be placed near sleeping areas. An alarm in the basement might not be heard when people are sleeping.

    Mark H
  • CO is lighter than air and tends to accumulate

    at what I call head to bed. Head standing up bed lying down so the detector should be in that area.

    The exception with CO is in cold environments and as it gets colder the specific gravity gets higher and heavier. At around 60 to 70 degrees it is about .967 just lighter than air which is 1.0. At temps around 30 degrees it is actually heavier than air at around 1.237. This can make a difference in boiler and furnace rooms with air openings into the room and when it is real cold it will be like LP gas and accumulate at the floor. I learned this the hard way many years ago.
  • jp_2
    jp_2 Member Posts: 1,935
    keep in mind

    though CO is lighter than "air" air is just a so-called molecule.

    air being 78% N2 which has the same weight as CO, then the 20% O2 in the air weighs a bit more than CO.

    So, if this saying were true, all the oxygen would be on the floor! but is it? Nope.

    can't discount the mixing that goes on in the air, a cigar burning shows this quite clearly, it all goes up cause its warmer than the surrounding air(hot air balloon) but far heavier than the surround air!

    air, by no means is still.
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