A method is described for deploying one or more illumination devices. The or each illumination device is self-contained and has a first state in which it is inoperative and a second state in which it is operative to provide illumination at at least one frequency within the range from and including infrared to and including ultraviolet. The method comprises the steps, optionally repeated at intervals, of: actuating a mechanism to move a said illumination device from a housing storing one or more illumination devices to an exposed position outside the housing; and automatically changing the state of the illumination device from its first state to its second state as a direct result of movement of the illumination device from within the housing to the exposed position.