Carbon monoxide detectors/alarms save lives.   This is without question; however, correct placement is essential for early warning of the presence of carbon monoxide (CO).   

Unfortunately there is a lot of confusion and misinformation about best placement for carbon monoxide alarms; with many believing they should be fitted close to the ground based on a belief it is more dense than air - but this is not correct and in fact the density of carbon monoxide is slightly lower than our air, so it will float not sink; thus, low placement of a CO alarm should definitely be avoided.  

Similarly, we see many CO alarms fitted centrally, half way up the wall - and while this is substantially better than fitting it low down to the ground, it is still not sufficient for early warning of the presence of Carbon Monoxide.  Thinking logically; if it's only half way up the wall, the top half of the room is going to need to be filled with Carbon Monoxide before it is going to reach the CO alarm.   On this basis, it is important to fit the alarm at a sufficient height that early detection can be given. 

Where does a Carbon Monoxide alarm need to be fitted?

If you have a combustion appliance fitted, be it a wood burning stove, and open fire, a boiler, a water heater, powered by gas, solid fuel, oil or similar - anything that uses a flame to achieve the desired result - should have a Carbon Monoxide alarm fitted within the room of the appliance.  

Ideally, we would suggest it is good practice to have Carbon Monoxide alarms on every level of your home if you have any combustion appliance in the property; better safe than sorry!   But at very least, a CO alarm should be fitted in any room with a combustion appliance. 

Of course, the focus of this article is on correct placement with solid fuel appliances such as open fires, wood burners and multifuel stoves.   But if you have a Combi Boiler or similar, you should certainly still have a CO alarm fitted. 

How high should a Carbon Monoxide alarm be fitted?

Where there is an open fire, wood burner or multifuel stove, your carbon monoxide alarm should be fitted high on the wall, or indeed on the ceiling like your normal smoke alarm.   

Section 2.36 of Approved Doc J in the building regulations suggest when fitting a carbon monoxide alarm on the wall, it should be fitted as high up the wall as possible, leaving 6" (150mm) above to the ceiling; or if fitting the CO Alarm directly to the ceiling, it should be spaced at least 12" (300mm) from any adjoining wall.   

It is also worth noting it is best to avoid placement above windows and doors, as the additional air circulation in these locations could hinder the effectiveness of Carbon Monoxide detection; but in some cases it is necessary to place them in these locations and ensuring they are fitted as high up on the wall as possible (whilst maintaining the 6" / 150mm gap from the ceiling) helps to mitigate this. 

How far from my fireplace should the CO Alarm be fitted?

In terms of distance from your fireplace; the UK building regs state the CO Alarm should be fitted at least 1 metre away from the fire (measured horizontally), but kept within 3 metres of the appliance (again being measured horizontally).  The minimum distance of 1 metre effectively minimises any false alarm issues when refuelling, while the 3 metre limit ensures better chances of early detection by restricting how far away from the appliance the detector should be location. 

Please refer to the diagram below from HETAS for a clear understanding of best practices for positioning of your CO Alarm.