The Fresh Air Fan is a wall-mounted home ventilation system designed with “one-way flow” to circulate and filter air. The composite HEPA filter is effective against particulate matter, PM 2.5, pollen, odors, etc. It uses ultraviolet and negative ion disinfection and sterilization technology, which is effective against bacteria and viruses. In addition, when it is cold outside, a heating function warms the air as it filters it to match the indoor temperature. The fan monitors indoor air quality and automatically brings in fresh air as needed, and functions can be controlled via the accompanying app.