UK law requires that emergency routes and exits that need illumination must be provided with emergency lights of adequate brightness should the lighting fail. So basically, if you need conventional electric lighting to carry out your business safely during hours of darkness then emergency back-up lighting must also be provided.
People often mistakenly interpret ‘hours of darkness’ as being equivalent to ‘during the night’. There are many daytime ‘hours of darkness’ throughout the average British winter.
Emergency Light Servicing
Emergency lights must have a full duration test every year. This means if the emergency lights back-up should provide 3 hours of illumination (which is common), they need to be tested for the full 3 hours to make sure they’re still working at the end of the test.
A ‘competent person’ can carry out this test however should a light fail the competent person should ideally have the skills to replace the faulty unit straight away.