Bio-Shield UV-C Air Sanitizer fixtures are designed specifically for installation in HVACR applications. On existing systems, infestations always exist. Therefore, the best results are obtained when the light is located downstream of and facing the coil. In this location the user can expect the highest efficacy in eliminating surface (coil and plenum), drain pan and airborne microbes. On new systems, it can be placed either up or downstream of the coil and aimed at the coil.