UV lamps are not a substitute for chemical disinfection. UV lamps need to be checked periodically to confirm their effectiveness and must be clean and devoid of debris in order to work properly. Chemical disinfection should always be performed, regardless of the absence/presence of a UV lamp.
The UV light should only be utilized when nobody is in the room. Do not turn the UV on if you have finished your work but are staying in the room, especially if you cannot close the sash. Prolonged exposure to UV light can cause skin cancer and cornea burns. If you leave the UV light on after finishing your work, post a sign outside the room to warn others. If you need to work in the room, switch the UV light off as soon as you enter.