CO/smoke detector placement

[kaohao]

What are the general guidelines for the installation of such devices with regards to fuel burning appliances? I am using two types of CO detectors. The system sensor COSMO and a stand alone device from interlogix (esl safe air 260-CO). The stand alone device's instructions say that they should be installed on the ceiling of rooms containing fuel burning appliances but not within ten feet of such appliances. The COSMO says not to install near furnaces etc. either. My problem is that the furnace rooms in this house are quite small so detectors can only be placed within a few feet of a fuel burning device.

 

[RAL]

I wouldn't worry too much about not having a CO detector in the same room as the furnace.  While it might seem that that would be the best place to detect CO as early as possible, it isn't necessarily so, especially if you have a forced air system.  A failure in the heat exchanger that allows CO to leak out will blow it into the ducts and then to the living areas first.
 
The most important thing is to place the CO detectors in the spaces where people are, especially bedrooms.  They are sensitive enough that they will give you ample warning before CO reaches dangerous levels.

 

[cobra]

If your furnace rooms are small, but are attached to larger basements, for example, you can place one farther away in the basement, so you know it does not accumulate a dangerous level of CO.

 

[Del91574]

Adjacent locations are fine, but bedrooms and sleeping areas are the main areas to place them. 
 
CO is essentially the same density as regular air, so the same mounting guidelines as smoke detectors apply. Don't buy into the outlet height mentality.....
 
The main reason for the distance is all fossil fuel burning appliances generate CO, and with a furnace or similar, when you start them up, you're instantly going to generate a "puffback" of higher concentrations that diffuses.