Repa Market 4 Inch Backdraft Damper – Inline Duct Backflow Preventer with Gravity Flap – PVC Backdraught Shutter for Bathroom Fans, Extractor Fans, Hydroponics, HVAC Ventilation Systems

We had problems with the fan in our laser getting covered with a layer of black shiny creosote. Had to flake off with screwdriver. After thinking about it we thought maybe the damp air was turning the dust from basswood into a coating. IT WAS! Get this for venting a laser, keeps moisture out and cold air from coming in through your vent.

Solved my back draft issue on a portable ac / heater exhaust duct where outside air was flowing in the home when the unit wasn't active.

Good dampers but really bad packaging. In a bag instead of a small box and because of that your damper gets delivered in pieces and is a pain to get back in. Plus it gets thrown all in delivery truck's and breaks.

Correct size. Small broken section on plastic joint line, however it did not hinder installation nor operation.

This Backdraft Damper has exactly 4"diameter an does not easily fit over or inside 4" connecting plastic pipe, I would recommend some kind of tapered inflow end to fit the connecting piping, if possible. The rotating flap is easily dislodged from the supporting mounts and can fall down into connecting pipe during installation.

I installed this product in the end of the vent tube on a bathroom vent. It works well and I am very pleased with it. Note, the flap pops out easy if the tube is flexed while installing. I had to put it back in three or four times while working the piece into the vent tube. It would be nice if the hinge was mechanical instead of a press fitting.

It stops most of the draft from coming back into my dryer so clothes don't cool off as quickly in the winter

Slid right in, flap works with the air blowing at 100%. I would recommend having the duct cleaned out to be sure the airflow is at 100%. It's amazing how much built up lint was in there. Fully blocked.