A system and method for sanitizing a target space include an ultraviolet (UV) lamp, an occupancy sensor, and a control unit operably connected to the occupancy sensor and the UV lamp. The UV lamp is configured to emit UV light into the target space. The occupancy sensor is configured to monitor the target space and generate sensor signals indicative of an occupancy of the target space by at least one person. The control unit is configured to receive the sensor signals generated by the occupancy sensor and to modulate an irradiance of the UV light emitted by the UV lamp over time based on the occupancy of the target space.