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Stop back flow bringing smoke to the rest of the house through the AC ducts? Answered

One room in the house we smoke, but when a window is opened all the smoke is sucked through the ac ducts to the main intake which is in a hallway right outside all the bedrooms.

I believe this is because the room is generally ~10 degrees warmer than the main part of the house which the hallway is off of because it is a large, open area which is less insulated because of a vaulted ceiling and many large windows.
I am looking for a way to seal the room off from the rest of the house without disabling the functionality of the AC/Heater.
I've found this HVAC Damper which I think could work, but it's a bit pricey, and it's supposed to be hooked up to a controller unit, so I don't know if there's a way to hook it up to either the fan or thermostat so it just opens when the AC/Heater/Fan is on, and the closes after.

I had also been thinking about building a box with a large, one-way valve, but the only design I can think of is a bit beyond my fabrication abilities.

Any help, hints, or suggestions would be appreciated, thanks.



Best Answer 6 years ago

Put a large fan or box fan as near to the window as you can get it and face it outwards. The fan should create enough pressure to draw the smoke from the room and out the window, overcoming the draw of the A/C return air vent in the hall.

I'd thought about that, but I think it would have to be pretty strong, and have the rest of the window blocked off, so it's just the fan part in the opening.
I've taped off the vents as a temporary measure, and with only some small crevices for it to get through, it still dumps a bunch of smoke in the hall.

So you're saying that when a window is opened, the air is sucked from the bedroom (where you are smoking) through the AC vent and into the other parts of your home?

If so, you can purchase large carbon filters and cut it to fit the opening of the AC duct in the bedroom so it will absorb any smoke and prevent it from getting through the house. The only thing you'll have to do is replace it on occasion when it no longer absorbs the smoke. 

To improve the appearance, you can always get a vent cover for the AC duct so that the filter is behind it, and for added benefit, you could close the fins on the vent cover (when you don't need the AC).

Yes, that's correct.
I am not familiar with carbon filters. How often would they need to be replaced?
I would have to make a really good seal around the edges of the filter, but I would have to balance that with the ease of changing them if it's often.
Do you know that specific product? It doesn't have any dimensions and I would need to make two for the two vents in the room.

Carbon filters are used in many things, such as AC units, Air Filtration systems (Air cleaner units), on Recirculating Air Stove Vents (where there is no outside venting). They are different from a basic furnace filter (which only traps particulates like dust), a carbon filter actually absorbs the chemicals and smoke, which is why they are used in air cleaners, and for stoves that have no outside venting.

If you go to any store like Home Depot, you'll be able to find a variety of carbon filters. The one I linked to was just to give you an idea of what they look like (because they are also sold in tube shapes for specific units). The products that you'll find are merely the replacement filters, and you should look for the best price compared to the size you can get. Then its just a matter of trimming the filter to the size you need.

As far as changing them out, it totally depends on how much they will filter. For example, a recirculating vent filter that is used on stoves that don't have a range hood, or access to outside venting, use a carbon filter, and on average, they last about 6 months with regular use. So it should last just as long for your needs.


6 years ago

The best solution is to stop smoking. You save money, you save your health and then you can put your efforts to something more constructive than trying to defeat the bad health effects of smoking.

Thanks, and I know, but until then this is not very helpful. Besides, it's not just me, I said it's a room where WE smoke.

When you open the window in the smoking room you make that room easy to draw return air from. The rest of the house is sealed up tight and the return air will pull air where it is easiest.

So to fix the problem put a fan in the open window to blow against the air flow and exhaust the smoke.  And, open a window on the other side of the house so the return pulls air from there.

I don't understand it, can you draw a diagram?
(with arrows)