A fluorescent tube is a long, thin type of light that is attached to fittings on walls and ceilings. The tube works by exiting mercury atoms with electricity to produce visible light. If the light starts to flicker, or if only one end of the tube works, the starter will need to be replaced. If the light doesn't turn on at all, you will need to replace the entire tube. The light's instruction manual will advise you on the size and type of replacement fluorescent tube required.
Clear the floor area and make sure all children and pets are out of the room. Turn off the light switch, and allow the tube to cool for several minutes. Turn off the main power switch for the circuit, located in your home's central consumer unit.
Place the ladder directly underneath the fluorescent bulb.
Remove the fluorescent tube's cover glass (if applicable), by gently pushing upward on the glass cover, then tilting it toward you. Some glass covers are held in place by screws at each end of the support bracket; unscrew them with a suitable-sized screwdriver.
Hold the edges of the tube gently and twist it toward you to release. Some models have tubes that require the end support brackets to be gently pulled apart in order to allow the bulb to come free.
Slide the new fluorescent tube back into the fitting by lining up the grooves on the end of the bulb and gently slotting it into place. Twist the tube to lock it in. Replace the glass cover. Switch the main circuit and light switch back on.
Replace the starter if the light still isn't working; the starter is located in the fitting racket. Repeat steps 1 and 2. Press the starter inward, turn it so that it faces away from you, and then remove it. Insert the new starter, push it into place, and it turn toward you to lock.