A heating, ventilating and air conditioning (HVAC) unit. The unit comprises a heat exchanger or drain pan located inside a HVAC housing that has one or more access openings and ultraviolet light-sensitive components therein. The unit also comprises a light located inside of the HVAC housing and a light shield located between the heat exchanger or drain pan and the light source. The light source includes a network of open-ended cells, each cell having ultraviolet light reflective walls. The light shield is oriented to direct an ultraviolet light from the light source through the open-ended cells towards the heat exchanger or drain pan and away from the one or more access openings and ultraviolet light-sensitive components.