Lochinvar & A.O. Smith 100157733 Power Vent Kit is a venting accessory designed to safely expel combustion gases from compatible gas-fired water heaters and boiler systems. It works by using a powered fan to move exhaust gases through the vent system, ensuring proper airflow and reliable venting even in installations where natural draft is insufficient. https://www.partshnc.com/power-vent-kit-3