New legislation came into effect on 1st October 2015 regarding smoke alarms and Co2 alarms in rental property. While it is legally a landlords responsibility to provide a Co2 alarm in any room where there is a solid fuel burning appliance, the law does not consider gas or oil a solid fuel and so doesn't cover gas boilers for example. This 'grey' area is dangerous in my eyes and my rule is that if you have gas or oil in your property, fit a Co2 alarm.
A typical Co2 alarm with a 5 year battery life will cost between £25-35 to supply and install. Failure to comply with the legislation could lead to fines of up to £5000! Even if you don't have what the law describes as 'solid fuel' is it worth taking the risk?