All rented accommodation should have smoke alarms throughout the occupancy and checked regularly. The alarms we use are powered from the mains, are interlinked and have a lithium battery backup, thus eliminating the occupier taking out the battery at Christmas time for that toy that didn't come with battery.
It's a good idea to have smoke, heat and carbon monoxide alarms throughout all households, some insurance companies insist on it.
Registered with AICO as Expert Installer, see https://www.aico.co.uk