It is a fairly obvious statement and most houses that I visit are fitted with them but very often they are not in working order. Quite often the batteries have been removed to prevent false alarms when the toast burns. Alarms should be tested regularly in accordance with the manufacturers instructions and you must ensure that they are installed in the correct position.
Detectors do not last forever and some should be changed at least every 10 years. Ideally install new detectors when moving into a new home – it is only a very small cost on the scale of things. Also consider having linked alarms.
So;
Install new alarms when moving home
Test batteries at least once a month
Fit at least one alarm on each level
Contact your local Fire and Rescue Service to request a free Home Fire Risk Assessment. Further guidance is also available on the UK Fire Service Resources website at www.fireservice.co.uk.