Abstract: In an example method of purifying air, steps may include: using a motor driven fan wherein the motor has at least two speeds; using an indoor air handling system with the motor driven fan and with a baffle that has at least an open and a closed position; installing a bypass for air to flow through a constricted space around the baffle, so that air can flow past the baffle when the baffle is in the closed position and through the bypass and back into the air handling system; and disinfecting air in the bypass using a UV lamp and a photocatalyst.