You will need more than one detector.
Carbon monoxide detector distance from furnace.
Keep the area ventilated to prevent unwanted alarms.
Because carbon monoxide is slightly lighter than air and also because it may be found with warm rising air detectors should be placed on a wall about 5 feet above the floor.
In small homes where 20 foot distance is not possible place the alarm as far away from fuel burning sources as possible.
If you have an enclosed garage directly attached t o the home then you should also place a.
In short you should place your carbon monoxide detector at least 15 feet away from your furnace and this same rule applies to all other combustion appliances.
If however they are more than 30 feet apart.
Avoid kitchens garages and furnace rooms.
How far should a carbon monoxide detector be placed from a furnace or boiler.
The detector may be placed on the ceiling.
Feet apart or less then place one in the middle.
Homes with attached garages.
Do not place the detector right next to or over a fireplace or flame producing appliance.
Keep units at least 20 feet 6 meters away from common sources of combustion particles.
The main thing that you are trying to avoid here is false alarms.
Make sure you don t install any co detector too close to any appliance that generates heat.