placement of CO2 monitor/alarms

[whiskeyrichard]

Should CO2 monitors/alarms be placed near the floor or near the ceiling for best/earliest detection?

We currently only have one CO2 alarm in the house. It is on the ceiling in our bedroom which is upstairs in a two story house.

I was thinking about getting a monitor as well and was not sure the best place to put it.


Thanks,
WR

 

[Gunner]

If you still have the manual check what it says. It is general recommended to put it at ceiling level outside the sleeping area.

 

[Rhone]

This was just on a show and I'm assuming you mean CO as in carbon monoxide. They placed units on the ceiling, middle, and floor level. They also had some units over 6 years old and ran them through a test. The ones on the ceiling went off first, followed by middle placed, followed last by floor. The units that were over 6 years old, one didn't go off, the other went off much later than any others. Their explanation for why the ceiling ones went off first was, that CO is a byproduct of combustion which makes heat. Heat rises, and took the CO with it which is why the ceiling units went off first, followed by middle placed units, followed by floor.

As gunner says, read your manual for best places. Make sure there's some on all floors, especially if you have a chimney with multiple flues because you can have the exhaust of one appliance coming out your chimney only to be sucked down the flue of another appliance and accumulate CO on a different floor than the one creating it.

 

[Jay H]

See my thread about CO detectors...

https://www.hearth.com/talk/threads/5633/


p.s. CO2 is carbon dioxide, CO is carbon Monoxide which is what you have a detector for.

Jay

 

[tjg911]

i am surprised about placement. since CO is heavier than air, i thought that they always go down near floor level.

i heated my prior house and this one exclusively by woodstove. i never had a CO detector in either house tho i have many smoke alarms in this and the other house. if i asked the volunteer fire department guys, i know they'd say yes they work and you should have them. are CO detectors reliable? i wouldn't think of not having smoke alarms and since CO is odorless, colorless and deadly it seems i should buy one but for some reason i thought i read (several years ago?) that they were not worth having.

opinions?

tom

 

[Gunner]

Don't know why everyone things CO is heavy?
CO is lighter than air at .97 vapour density.
But because it is so close (.03) to room air it mixes readily at all levels in a house.

Propane on the other hand is heavy at 1.52 vapour density and helium is lighter.138

CO detectors are required by law in many areas, so yes they are worth having.

 

[Gunner]

(broken link removed)

 

[tjg911]

Don't know why everyone things CO is heavy?
CO is lighter than air at .97 vapour density.
But because it is so close (.03) to room air it mixes readily at all levels in a house.

Propane on the other hand is heavy at 1.52 vapour density and helium is lighter.138

CO detectors are required by law in many areas, so yes they are worth having.

i always heard that CO was heavier than air, that is why there's a step down of 3-4" in the garage so the CO collects at that level vs having the garage floor at the same level as the walkin basement. not saying you are wrong, just that was my understanding.

tom

 

[Rhone]

The reason it rises, is that CO is coming off a flame/hot source. Think of it like smoke, if I'm not mistaken smoke particles are heavier than air. But why do we put smoke detectors on the ceiling? The answer is pretty obvious because we can see that the smoke particles, CO, and air coming off has absorbed the heat of combustion and become less dense than the surrounding air. It being less dense because it's hot rises to the ceiling first, and from there it spreads out, and as it slowly cools it drops to the floor. I'm not particularly good at explaining things, but I hope that makes sense. Think of it as if the CO is being released at 175F... it being about the same density as air it's going to rise up because it's hot and set the top detectors off first which is what the show said... similar to why smoke rises I think, though the show didn't mention smoke or if smoke is actually more dense or less.

 

[Jay H]

So, if your CO detector is not in the same room as the wood stove (or any other heat source) it is preferred to place them near the floor?

Jay

 

[Rhone]

No, basically think of how smoke travels. Imagine lighting a fire in a fireplace with the damper closed. The first thing that will happen, is the ceiling in the room you're in will fill with smoke. Eventually, the smoke will find its way out to the hallway and other parts of the house travelling across the ceilings. Eventually, it will start to fill up so much it'll start to fill in the middles of the rooms, and lastly the smoke will hit the floors. CO does the same thing because CO is hot that means it's less dense and wants to rise and spread around the ceilings first, but as it cools it starts to lower and set off ones placed in the middles of walls, and lastly when you house is really full it will set off the ones at the floor. So, the ceiling is the best place regardless. In the show, the detectors were placed in a room down a hall from the CO source and in that room they went off in the ceiling first, then middle, then the ones at floor level.

 

[Homefire]

So, if your CO detector is not in the same room as the wood stove (or any other heat source) it is preferred to place them near the floor?

Jay

My owners manual speaks to placement
as between 3 and 4 feet off the floor in
a room away from the fire where you
can hear it if it goes off.

 

[Rhone]

Homefire, that's a good point I would place it whereever your manual says to place it. I found this site http://chemistry.about.com/od/howthingswork/a/codetectors.htm that also says that it rises to the ceiling first and spreads that way but that 5' off the floor is the recommended location. Intersting, and many others state CO detector placement is not as critical as smoke detector.