How long should I leave the emergency light on while doing my monthly test? Need the reference as well please. Thank you. F

No fixed duration, just long enough to be able to check all fittings have illuminated. For example if an installation has separate test switches for each room, corridor section, stair, etc then it could be very short, e.g. a small room with one or two fittings and a test switch might only take a few seconds, or longer, e.g. a building with no test switches or just one at the main incomer might need 10 or 15 minutes to be able to get around al areas.