Check Valve Damper

This flip valve is perfect for ventilation systems.

What this device does is it automatically closes the duct when you stop using the extractor in your grow, avoiding any sort of insects or other objects getting in or out, as well as avoiding any air from your grow getting out and stinking up the place if you're using an extractor.

It’s basically a hatch with a spring that’s only open when the air flow is going in the first direction, avoiding the air reversing or any insects being able to fly back in.