Fresh Air Handling Unit (FAHU) is an excellent solution for regulating and circulating fresh air as part of an HVAC system and it ensures a constant flow of fresh clean air and a very well-conditioned environment. They take fresh ambient air from outside, clean it, heat it or cool it, maybe humidify it and then force it through some ductwork around to the designed areas within a building. Most units will have an additional duct run to then pull the used dirty air out of the rooms, back to the AHU, where a fan will discharge it back to atmosphere. Some of this return air might be recirculated back into the fresh air supply to save energy.