4 Inch Draft Blocker Backdraft Damper Duct Draft Stopper One-Way Airflow Ducting Insert Backflow Preventer Inline Fan Vent Deflector

Each time the A/C or furnace kicked on it would draw outside air in through the vent hood. Cold in the winter and hot in the summer. The temperature under the hood was significant and very noticeable. So I installed this draft blocker in the pipe in the attic, separating the pipe at a joint inserting the valve and reconnecting the pipes. I seal the joints with aluminum tape. The draft blocker has a weather strip inside sealing it when not in use. I did have to reseal the pipe where it passed through the roof with roof tar to restore the water seal. It works great, the is no back draft now when the A/C is running and made a huge difference. I would recommend and buy again.

These work great for what I need them for. They open and close a few times a day and have been working that way for about seven months now. Simple to install not much else to say.

Works well and looks nice. Quality product

Works well, makes a tight seal, no tapping sound when the flaps close, a little undersized for 8 in hvac. But not so much that some hvac tape couldn't seal it. Easy to install. Seems like it will hold up for a long time. Decent damper for the price.

perfect fit

Works very good just make sure if they’re installing it. It’s tilting upward in the hose a little bit so the damper says shut.

nice ,it works.

If this vent is installed with the air flow going down, the springs will be challenged to close the vent due to the weight of the fins. Likewise if the orientation is horizontal with the hinge flap horizontal, the spring will struggle. The construction and fit is solid with a good seal when closed. Will do the job keeping in mind these conditions.

Excellent design, construction, and workmanship. The shell is made of rigid sheet metal and the butterfly dampers of aluminum. The dampers are normally held in the closed position against the seal by light springs. The dampers open in one direction by just blowing against it. Both ends of the shell fit perfectly inside 4 inch diameter ducting. The plain ends allow it to be easily installed in an existing ducting that needs a backflow preventer. It even had a sticker noting how to orient the dampers properly when installing it horizontally. I used it to prevent wet exhaust from our clothes drier backflowing to our washroom. Both drier exhaust and washroom vent were tied to a tee that exhaust to the outside. Our washroom vent fan damper was not enough to keep moist air from our drier from backflowing into our washroom.

works great for my microwave vent

Good quality - feels like it will hold up to regular use. We attached it directly to the outside vent which has louvers. Since the flaps open proud of the outside opening, we taped it so the flaps would not bump up against the flaps while in use. I feel like I should use some sheet metal screws to hold it, but the fit is snug and the tape seems to hold it all together.

I'm using this to stop cold backdraft from exterior dryer vent. It has diminished the inflow of cold air in the winter but has certainly not stopped all cold air flow. Location: Northern Ontario

I have allergies and apparently if I leave my portable Danby AC connected to the Window I wake up wheezing with Asthma or rather a type of bronchitis that fills my lungs with mucus from the allergies. Coughing and wheezing throughout the night. I had no idea that a backdraft damper existed or at least I could imagine that it existed but I had to search for "AC Duct air Blocker" to find that what I was looking for was a backdraft blocker. Measured twice the size of my Duct and it turns out that there are only three sizes 4", 6" and 8". My duct was 6.5". When my Draft Blocker arrived and I fitted it into the duct it was loosely fitted so I added a foam seal around the draft blocker and that made the backdraft blocker a tighter fit. Wasn't sure how far to push it into the duct but on the first try I decided to just have it near the entrance of the duct and that should be good enough. Checked that it was closed when my AC is not on and checked that I had Air flow when I turned on my AC by checking outside whether there was hot air blowing out of the exhaust. Yup works wonderfully. SOOOO theoretically without the outside air flowing through my AC duct I should have a good sleep tonight. I love how that if I have a problem such as a Backdraft on my AC Duct that I could find it on Amazon.