We use a high-powered Hepa Vacuum system (negative air machine) that is connected via an access close to your furnace unit. From each register and return vent, a high-pressure compressor is used to blow/brush dirt, dust, and debris down into the vacuum system. Afterwards the ductwork is fogged at each vent with a safe disinfectant which kills mold, bacteria, and viruses. And all register/return covers are cleaned and put back on. Includes up to 13 vents.