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Your cart is empty.Filter Lock Furnace Filter Slot Seal by Allergy Zone is a patented, one-size-fits-all product that covers the filter slot/door to prevent entry of unfiltered air into your heating and air conditioning system (HVAC). Used by HVAC, energy auditing and weatherization professionals to stop air leakage, enhance HVAC system integrity and improve the performance of 1-inch air filters. Stopping air leakage improves indoor air quality and reduces energy consumption. Filter Lock installs in seconds without any tools. The built-in magnets attach Filter Lock to metal duct work and hold it securely in place. Use Filter Lock with any 1-inch air filter measuring up to 25" Long.
Experienced Reviewer
2025-09-03 18:42:13
This is an amazingly simple invention that finally solves a problem that we had in our house. The area where I slide in my filter in the furnace had big gaps on the sides, top and bottom. To make matters worse there was an opening on both sides of the furnace so that you could install the filters from either side. So the air was getting sucked in from both sides and probably very little was coming in from the cold air returns.It is beyond me why furnace installers have not figured out a way to fix this problem. I thought about calling someone to build a door or rework the metal so that there was a tighter fit but that would have cost a fortune. This little invention while perhaps not perfect, improved the situation 99%. I still may be getting some air going around the filter inside the cover but at least my system is relatively closed off so I am getting better air flow and I would not be surprised if this cuts down on my bills over time.This consists of two pieces of heavy duty plastic that measure 4.5" x 14" each. The plastic reminds me of the type that you would find on a pool liner. It's pretty tough but flexible. There is a magnetic strip inside the plastic on one end of each piece and two that run up each side. The magnets inside the plastic being broken into pieces allow you to fold them over in a couple places to get a good fit on your duct.Depending on how your duct work is constructed this may work better for some than others. I would urge you to take a look at my photos and then take a look at your ducts to see if this will work for you. For me it works perfectly at the bottom but at the top the way they constructed my ducts I have to fold it over and put it on a slight diagonal.I found that the magnets were strong enough to stick to my duct work but pliable enough that I could bend them at the top where I had issues with the way they fit in order to get a tight seal. They come in two pieces so that they can bend over on each side and still get an exact fit for a variety of sizes. The two pieces overlap enough that there is no air escaping. My filters are 16" at the opening.One thing I may do to make changing the filters and re positioning the covers easier is to tape the top edge and the bottom edge to the duct. It's not such a big deal for the bottom, but the top edge is wedged in to fit my odd fitting duct work so I think if I did not have to remove it completely to replace the filter that these will maintain a good fit longer.I felt these were a decent value for what I paid ($8 each) I had to buy 4 so it was $32 but I would have spend a lot more had I called someone to rework the duct area and install a cover. Plus some covers still do not seal off the opening completely.Thanks for reading my reviewBecky Brooks*I paid full price for this item it was not a free sample
Nathan C
2025-08-17 13:06:49
I saw a youtube video for this product and the demonstration of the product described my issue perfectly. I ordered this product and recieved in a quick manner. Installation was super easy just takes about 5 mins to get it on the and adjusted to what you need on your particular HVAC system. I will say that there is no more musty basement smells when the system is running! It completly seals the filter housing.
Putertech
2025-08-10 09:06:00
It does exactly what is claims, and that's a great seal for you slide in filters
T. Soptick
2025-07-13 13:35:14
Works great. Installs easily. Magnets in this cover hold this item sufficiently. Bought it for the benefits listed, but also to prevent cigarette smoke spreading through out our house. We have a family member who smokes and is not allowed to smoke in the house. So during the winter she smokes downstairs in our unfinished basement near the furnace and the smoke goes up the furnace ducts and spreads throughout the house. Not anymore! Highly recommend!
Mark Hughes
2025-07-03 18:19:51
I really wish I would’ve found these earlier. I don’t have much of a gap between my intake and my air filter but I thought I’d give these a shot since my furnace is in the basement. I could tell as soon as I put these on that the intake was working much better and I didn’t have to worry about pulling in any of the dust or material from the basement into the filter, especially since our litter boxes are in the same room. I’ve noticed after a few weeks that my filters are much cleaner now as well they will allow me to have our filters last longer there by saving money. I highly recommend.
OneGoodSoul
2025-06-14 20:58:41
Needed these to cover a small gap where our filter sits into the furnace. It now complete blocks off any air the furnace would pull through that gap and stop that air from bypassing the filter. It is made of flexible vinyl and has magnet strips inside around the edges.
CSM
2025-03-09 10:19:26
After watching the video for the installation I thought this would be a great solution for closing off the filter opening. The 2 pieces needed to be overlapped and the magnetics did not grasp each other as easily as shown in the video to get a tight closure. It works that it does cover the filter door but was expecting a little more. They should consider 1 piece options by length needed to eliminate the overlapping problem. Just my opinion with my situation.
Celt
2025-03-03 17:11:56
Yes this is an easy fix to replace that old crimpled slot sliding cover. Having said that, if you have a 25" slot to cover it will not wrap around both sides to get a complete seal. If your slot is smooth and never had a sliding slot cover, then it will exactly cover the open slot. So I have about a 1/3" unsealed at one end, but I believe that opening will be negligent. No regrets about purchase but highly suggest the manufacturers make those two pieces an inch longer apiece.
Janjie Unciano
2025-02-26 13:38:11
Good quality and seems like it fill the gap on my Furnuce . Works well will buy again
CalgaryBen
2025-02-24 10:04:06
This was a quick product to slap onto the furnace filter opening, and it seems to work adequately well. However, I like to print the date on my furnace filters so I know when to change them, and this product (being opaque) obscures the view of everything. In retrospect, I could have saved some money and made my own seals -- do yourself a favour and buy some "magnetic tape" with a self-adhesive backing. Then get some clear plastic (clear plastic garbage bags would work well) and cut them to size (e.g. 4.5" x 18" for a 16" filter, or 4.5" x 27" for a 25" filter) and fit with magnets (cut a couple 4.5" strips, put them on, and then cut and put on long strips). Chances are you'll be able to make a few of these for friends and family using the roll of magnetic tape you bought for less money than a single set of these seals.
Got no instructions
2025-01-19 10:04:48
Good product fast easy to use and seal the filter area.
Brian D.
2024-12-05 11:24:09
Good fit ,easy to install ,covered the gap completely
Doug S
2024-11-15 16:35:57
seriously these should be 1/2 the price they are selling them for.
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