Where you have escape lighting this must be periodically inspected. This is a drain test of existing escape lighting units. The elements of the test include checking the lights and activating them as though there was a power cut. Lights must then illuminate for a minimum of 3 hours.
If the lights fail during this time, the most common failure is batteries. In that case we have found it more cost effective to simple change the whole fitting.
In all HMO properties it is essential that your occupants can get out safely in a fire and regulations mean that you as a landlord has a duty to ensure appropiate measures are in place.