Best CO (Carbon Monoxide) detector?

[Gewehr98]

We're going to get one this weekend.

My cousin called me, and had to evacuate his house yesterday morning when the CO detectors began shrieking in the middle of the night.  He changed the batteries, and they shrieked even louder, so everybody went to his daughter's apartment while he opened up the place and called the furnace dude.  The furnace dude said one or more of the burners were sooting up via incomplete combustion, etc.  That little incident was a wake-up call for me, my parents, and my sister. 

So I have 4 each smoke detectors and no CO detectors.  I'm heading to Menard's, and am curious which have the best reviews...

(I might buy an extra one and ship it off to Grandpa Shooter, too)

[Brad Johnson]

*edited to fix my misconceptions about air and the density thereof*

Kidde makes a unit that simply plugs into any outlet.  I got mine at Home Depot.

Brad

[brimic]

Kidde makes a unit that simply plugs into any outlet.  I got mine at Home Depot.

I have the same thing- plugged into an outlet near my furnace. I just changed the battery in it this last weekend because it was beeping obnoxiously to tell me it was time for a change.

[Nick1911]

Smoke is lighter than air so smoke detectors should be on the ceiling. CO is heavier than air so CO detectors need to be as close to the floor as possible.  A no time should they be higher than the lowest point your head will rest (i.e. your mattress). 

The packaging on my CO detector stated that CO is very close to the same density as air, and as such the mounting location didn't matter much.

[Azrael256]

it depends on the location of the furnace.  Mine and my mother's are closet units at the height of the living space.  For us, having it up high with the smoke detectors is useless. (We're all electric now, so we don't actually have them)

In our old house, the furnace was in the attic, so we had a combo unit on the ceiling next to the attic entrance in the hallway.  We also had a plug-in unit in that hallway just for good measure.

[Brad Johnson]

The packaging on my CO detector stated that CO is very close to the same density as air, and as such the mounting location didn't matter much.

*also edited to fix my misconceptions about air, CO, and the density of me*

I know a family that lost a pet from CO.  The dog slept on the floor and was discovered dead one morning.  The family remained completely unharmed and the CO detectors, plugged into an outlet roughly two feet off the floor, never triggered.  Slab house, closed doors, a poorly vented propane heater, and no ceiling fans or central HVAC fan to keep air moving. The CO pooled on the floor and smothered the dog in its sleep without ever getting high enough to trip the detectors.  That's how insidious CO can be.

*I called them to make sure and they confirmed both the vet and fire marshall said CO, so who knows.*
Brad

[Boomhauer]

Oh, and replace the CO detector on a regular basis- they have finite lifespans.

[MechAg94]

"Very close" and "equal" ain't the same thing.  CO is heavier than air, even if only slightly.  It will pool in low places like your basement, waiting to kill you dead.  If you have a modern single-story slab-type home with relatively tight doors it will pool on the floor.  If you have a significant CO leak and your bed is lower than the detector, you won't be alive to hear it activate.

I know a family that lost a pet from CO.  The dog slept on the floor and was discovered dead one morning.  The family remained completely unharmed and the CO detectors, plugged into an outlet roughly two feet off the floor, never triggered.  Slab house, closed doors, a poorly vented propane heater, and no ceiling fans or central HVAC fan to keep air moving. The CO pooled on the floor and smothered the dog in its sleep without ever getting high enough to trip the detectors.  That's how insidious CO can be.

In other words, mount your CO detectors as close to the floor as possible.  Put one in next to potential CO sources and one in EVERY every bedroom at some point lower than where your head will be as you sleep.

Brad

Are they sure that wasn't propane, and not CO?  Propane will stick to the low spots more than CO will.  Hard to believe the hot heater outlet air would not rise more.  I guess I am not accustomed to CO not mixing at all.

We have CO throughout most of our process at the plant I work at (it is one of our products).  We wear CO, O2, LEL meters outside at all times.  I have never noticed CO to pick any particular level off the ground.  It just mixes with the air and floats with the breeze. 

Just FYI, 25 ppm is the OSHA 8 hour exposure limit for CO.  I think something over 1000 ppm is immediately fatal.  There are other shorter exposure limits in between those. 

[cassandra and sara's daddy]

i'm paranoid  i have smoke co and explosive gas detectors in the attic crawl space main living areas and every bedroom. and if you want a shock set one off with a small kid asleep.  mine can sleep through em sometimes.i did the attic after an old fire marshal  pointed out that fires often start inside the walls and that the smoke can fill the attic first   the crawl space for the reasons mentioned earlier. propane is heavier than air and cleanup is a 2 square block area if you have a problem. the three wire to interconnect them was cheap  

[Nick1911]

Are they sure that wasn't propane, and not CO?  Propane will stick to the low spots more than CO will.  Hard to believe the hot heater outlet air would not rise more.  I guess I am not accustomed to CO not mixing at all.

I had actually typed up a long, heated post in response to Brad, but ultimately decided not to post it.

In the particular use case that Brad presented, it probably makes sense to mount CO detectors low to the ground.

In my use case, it does not.  I have confidence that CO at 120*F will rise and that forced gas heat will cause it to mix.  My bedroom is not on the ground floor.  We don't close the door at night.  As the gas furnace is the only unattended gas appliance I own, I do not feel that placing a CO detector 8' off the ground is inherently unsafe in my situation.

[brimic]

If you yhyave cold air returns near the floor by the source of the CO, the CO would get sucked in and redistributed throughout the house- but it will at least be diluted out....

[Physics]

CO is heavier than air, even if only slightly.

You sure about that?

http://www.webelements.com/

It just mixes with the air and floats with the breeze. 

I would agree with this.  CO is not going to fall, it is lighter than air, however they are very close.  CO2 is heavier than air however and will pool up in low areas.  I would mount a CO detector where the manufacturer says to install it.

[MechAg94]

I just happen to be doing an internal online CO safety thing right now and it says the density of CO is 0.97 (air = 1). 

For me, my heater is natural gas in the attic and uses central air all at the ceiling level.  I often run a ceiling fan on low just to keep the heat from staying at the ceiling.  My one CO detector at about 4 feet. 

I don't know what happened in Brad's case.  Reality is stranger than fiction often enough. 

[Brad Johnson]

Did some poking around to verify and sure enough I was WAYYYY wrong on CO being heavier than air.  Amend all previous assertions accordingly.

Brad

[tyme]

Fair enough.  I'm mystified over what happened to that dog, though, based on your description.

Any gas can displace oxygen and present a serious risk of asphyxiation.  People have died of asphyxiation in closed areas from LN2 and dry ice.

Air is primarily a mixture of N2 and O2.  N2 = ~28 g/mol, O2 = ~32 g/mol.  That's over 10% difference, but when was the last time you heard of someone in a loft asphyxiating because the oxygen pooled at the lower level leaving them almost none to breathe?  Diffusion and air currents keep gasses from separating out very much unless there is a larger difference in density than that.  CO is the same density as N2, so if anything, O2 would pool below the CO.  It doesn't, because of the aforementioned diffusion and air currents.

The dog might have suffocated from a propane leak... except that propane and NG producers add horrible smelling stuff to them precisely to make detecting leaks easy.  If it had been propane, they should have recognized the smell immediately upon waking up, and they would have been lucky they didn't suffocate as well.

On the other hand, if it was CO that killed the dog, then the CO detector must have been broken, and everyone nearby was very lucky they didn't die too.  If that's the case, it's mystifying how nobody else suffered any symptoms, because CO doesn't pool near the floor.  If it killed the dog it should have affected other people too.

[Regolith]

Dogs are smaller than people.  It's likely that everyone was equally exposed, but the dog died first because it got a larger dose per it's body size as compared to everyone else.

Remember the canary in the coal mine?  Same thing.  The canary dies first, because it's much smaller than people, giving the miners advanced warning to evacuate.

The dog could have also been closer to the source, giving it a larger exposure.

[Perd Hapley]

Did some poking around to verify and sure enough I was WAYYYY wrong on CO being heavier than air.  Amend all previous assertions accordingly.

Brad

[W. F. Buckley] Amend them yourself.  [/]   

[Gewehr98]

Have to agree with Fistful on that one.  (What's the world coming to?)

[Brad Johnson]

Edited *skulks off with tail between legs*

Brad

[MechAg94]

Dogs are smaller than people.  It's likely that everyone was equally exposed, but the dog died first because it got a larger dose per it's body size as compared to everyone else.

Remember the canary in the coal mine?  Same thing.  The canary dies first, because it's much smaller than people, giving the miners advanced warning to evacuate.

The dog could have also been closer to the source, giving it a larger exposure.

I was thinking the same thing.  The dog could have just been more sensitive. 

Also, the mercaptan used to odorize natural gas at least can be fairly subtle.  I have a natural gas stove.  Once I inadvertently left a burner on at a very low setting.  It later went out.  I didn't notice a gas smell until I went outside and came back in.  I shut it off and opened windows and such and there was no issue.  That bothered me and I am much more careful now and bought some detector stuff.  What I am saying is that a small, gradual leak can go unnoticed.  On the other hand, I had a leak out at the meter earlier this year and you could smell it from around the side of the house. 

[Gewehr98]

Dog = canary in coal mine? 

[Brad Johnson]

Dog = canary in coal mine? 

In my Rott's case it was more "bull in china closet".

Brad

[French G.]

Heh  Typical APS. A whole long page and one reply that came close, just that they had a Kidde, no reviews. Cue rambling argument about physical properties.

Of course I have nothing to add, never owned a CO detector. Just felt the need to add one more kazoo to the circus parade. 

[Brad Johnson]

Heh  Typical APS. A whole long page and one reply that came close, just that they had a Kidde, no reviews. Cue rambling argument about physical properties.

You expected otherwise?  Boy are you the naive optimist! 

Brad

p.s. - Kidde and First Alert seem to be the two most well known detector brands.  You probably won't go wrong with either.

[Gewehr98]

That's what I figured, and it somewhat depends on what I see for sale at Menard's this weekend. 

What would a thread be on APS without at least some drift?