The AirSupply 4 Inch Duct Fan helps with all of your ventilation issues. The ES4 inline fan increases the centrifugal airflow vortex of your ventilation system to remove heat and humidity from grow tents, electronic equipment closets, and industrial workspaces. The airflow direction is reversible and can be used to intake fresh air into space or exhaust hot air or fumes from your space. It can even be used to pull air through odor-reducing carbon filters in grow tents. Compared to old-school AC or DC motors, our brushless DC (also known as EC motor) and variable speed controller lets you precisely control your fan speed from 0-100% to increase efficiency while reducing noise and power consumption.