Crawl Space Basement Ventilator Fans : Airflow: 220CFM. Size: 18″ x9″ x2″. This crawlspace/basement vent fan is designed to ventilate out odors and pollutants, while reducing humidity levels to prevent mold in your crawl space and basement. Built-in Dehumidistat & Freeze Protection Thermostat : Operating humidity: 20%-80%RH. This crawlspace vent fan with humidistat features Durable Stubborn Aluminum Zinc Shell, Freeze Protection Thermostat, ideal for work in a humidity and a low-temp environment, don’t worry it rust. Powerful But Quiet Fan Booster Motor : <48dba noise. This register booster fan features durable centrifugal blades and ball bearing motor, cools and ventilates areas with its powerful airflow. Easy-to-Operate Vent Fan : Features knob control panel, easy to set time for running. Just plug it in, set it and forget it. Easy to exhaust vent radon gas, treated wood gases and odors, prevents migrating into living areas. Best Gift For Your House : Let this ventilator fan be the best helper for your house.