There's a strict legal requirement regarding smoke and carbon monoxide detectors that must be fitted in any property you are renting out.

Since 01/10/2015 all landlords have to have these alarms fitted in their properties, on each floor as well as a carbon monoxide detector in all rooms with a solid fuel burning device. The landlord has to ensure that every alarm/detector is in perfect working order at the start of every new tenancy.

Once a landlord has installed and tested the smoke and carbon monoxide detectors on the initial day of the tenancy,  it becomes the tenant's responsibility to test them regularly. Testing monthly is the recommended and if a tenant finds that their detector is not working they should make arrangments with the landlord for replacements.

It is now a landlords' duty to check that the all alarms fitted within their property are in good working order before a new tenant moves in.

These regulations are in place for the safety of all private sector tenants. 

It's reasonable for the landlord to write to their imminent tenant explaining that this is a legal requirement and that it's for the safety of the tenant.

If local authorities have grounds to believe that the landlord isn't complying with the regulations they will issue a notice detailing the suspected breach and the action they expect to happen to resolve the issue.

If the landlord is compliant or demonstrates that they have taken all necessary steps to become compliant within 28 days of the notice period they will escape a penalty which could be as much as £5,000.

It's up to the landlord to make an informed choice when it comes to the type of detector they fit to suit the property and the tenant ( battery powered or hardwired). Needless to say, the more detectors a property has the safer those living in it will be.