Abstract: An air conditioning system to improve indoor air quality (“IAQ”) comprises an air conditioner to receive indoor air from an indoor space and to heat or cool the air, the air conditioner to then return conditioned air to the indoor space. An IAQ option board (“IOB”), electrically coupled to the air conditioner control board, is configured to accept electrical inputs from at least one IAQ sensor. A fresh air damper is electrically connected to the IOB, the IOB controlling the position of the fresh air damper valve. An air purifier is situated such that air from the indoor space passes through the purifier. The operation of state of operation of the purifier is based at least in part on the input from at least one IAQ sensor to improve the IAQ of the indoor space.