People in your premises must be able to find their way to a place of total safety if there is a fire by using escape routes that have enough lighting. Where any escape routes are internal and without windows, or your premises are used during periods of darkness, including early darkness on winter days, then some form of backup to the normal escape route lighting (emergency escape lighting) is likely to be required.
In small premises, where the escape routes are simple and straightforward, borrowed lighting, e.g. from street lamps where they illuminate escape routes, may be acceptable. Where borrowed lighting is not available, suitably placed torches may be acceptable for use by trained staff. In larger, more complex premises it is likely that a more comprehensive system of electrical automatic emergency escape lighting will be needed to illuminate all the escape routes. Where people have difficulty seeing conventional signs, a ‘way-guidance’ system may need to be considered.