darkstar said:
sydney1963 said:
So i'm assuming CO rises as does smoke, correct?
Nope... CO is heavier than air, and odorless. CO detectors should be placed closer to the floor, which is why I am a fan of the plug-in ones. The combination CO and smoke detectors are, in my opinion, next to worthless. Smoke rises, CO sinks. You can have CO without a fire hazard condition. Therefore you stand little chance of detecting JUST CO with a combination unit.
---scott
I am going to disagree with you there. Co is marginally lighter than air as stated earlier and as a result mixes equally through the house based on prevailing currents. It does not sink but mixes almost even with the air and if anything will rise with air currents in your home.
I disagree 100% with plug ins being a better unit. In most cases we find that the plug in units constantly being unplugged for vacuuming etc. Also, the plug in units tend to be placed behind tables/couches/furniture where the air currents are limited, rendering the unit ineffective and useless. In my experience, I have responded to both units alarming as appropriate, but the cieling mounted ones tend to be out of sight/out of mind and left alone to do thier thing, unobstructed. You just have to remember to change thier batteries. As far as the combination units being next to worthless, I can say with 20 years of experience as a firefighter, those are the units I currently have at my residence and can think of situations where residents can say they owe thier lives to the unit functioning in one capacity or another.
The reason that you do not place the unit less than 10 feet from a device where combustion takes place is that repeated low dose exposure to carbon monoxide desensitizes the detector to the presence of CO and eventually will render the unit ineffective, so the theory of putting the unit right next to the stove is
not recommended. Co is a byproduct of combustion. When selecting a location choose a location between the device generating CO and where your habitation normally takes place. If you look at the detector packaging, you will see that there is a certain concentration where the unit alarms. If the unit alams at 35 PPM, a constant exposure to 10 PPM will make the unit less sensitive, and it will only alarm (over time) with a greater exposure to CO, which means when its time to really alarm, it may not. A smoke detector is designed to alarm with ANY smoke. CO detectors are not, as there are levels of CO that are considered acceptable, unlike smoke.
In mass, you should have a detector on each level of habitation, and there should be one in the room with the pellet stove. The code here also calls for a carbon monoxide detector within 10 feet from the outside of each bedroom (thus code could require more than one on any floor if there are 2 bedrooms seperated by a hallway of more than 20 feet) Remember that CO detectors have a substantially shorter service life than smoke detectors, so if you do buy the combination units ( I strongly recommend. ) you will have to replace them sooner
I hope this helps clear some of the common misnomers up about these units.
*edit*
notice in the last post it also has an autoignition temperature, as well as a lower explosive limit.
