How often should emergency lighting be tested?

In accordance with BS EN 50172:2004 / BS 5266-8:2004 emergency lighting should be tested both monthly and annually. The monthly test can be a partial discharge to test system functionality. The annual test should be a timed discharge to ensure that the battery set can provide at least 3 hours of backup time. All results should be recorded in a log book and the annual test carried out by a suitably qualified lighting specialist and/or electrical contractor and a certificate issued. The certificate may also be required for insurance purposes.