How to Find the Air Filter for the HVAC System in Your Home

Air Filter
It’s good to remember to clean your air filters so that the filtration stays clean for your home. (BanksPhotos/Getty Images Signature)

I can’t find the air filter in the HVAC unit in the home we just bought. Do all central heating and cooling units have filters?

All central heating and cooling systems should have an air filter, but it can be harder to locate on some HVAC units than on others.

It’s usually located in the return air duct or blower compartment before the return air reaches the air handler. This allows it to clean the air coming from your house before it enters the HVAC unit.

No matter where your air filter is, you need to change it every month during high-use seasons (like summer and winter) and once during the fall and spring. (mphillips007, Getty Images Signature)

Where to Look for HVAC Units and their Air Filters

Common locations for air filters in HVAC units include:

  • On horizontal HVAC units with the return duct attached to the side of the air handler, the filter often fits in a slot on the return air (intake) side of the unit.
  • On vertical air handlers with the return air duct entering on the top of the air handler, it often slides into a slot above the HVAC unit.
  • On vertical air handlers with the return air duct entering below the air handler, it often fits in a slot below the HVAC unit.
  • On other HVAC systems, it may be located behind the return air grill on a wall in your home.
  • On HVAC systems with a return in each room, one may be behind each of the return grills.

Further Reading


  1. I have a heat pump central heat and air system in my new home; it’s located in the attic. The return vent in the ceiling has a filter. When I inspected the unit, I noticed a slot for a filter there too. Should I place a filter in the unit as well?

  2. Danny,
    Wife and I having a few allergy problems. We have Aprilaire filters installed on both hvac units. I have made a visual inspection of vents and returns and they seem pretty clean. Recently had one of the hvac units replaced.Should I have vents cleaned? I’ve seem so much negative information about this that I not sure whether to invest money in it.

  3. I can’t seem to find the air filters on the horizontal gas heat unit in my crawl space. I did see grill panels with wires and tubing but nothing that looks like it belongs to a filter function. I did find filters inside the house. I called the Goodman Mfg. and they have no clue. The unit was made in 2000 and don’t know who installed it…any ideas?

  4. I wont to know if I have a filter on my AC air handler that is located in my atac which is separate from my condenser unit. I do have two return ducts that do have filters. but im not sure if the air handler its self may have a separate filter that also should be changed every season the hole unit is only 4 years old. THANK YOU I hope you can help me and may be give me and idea of where it is located

  5. do I really need in line vertical air filter and room wall inlet filters. the in line filter is 4inches thick and each room filter is 3/4 inch thick. isn’t this too many. all I need is the in line filter?

  6. Danny, you’re a life saver. I was panicking since I’ve had a similar problem as Paula. It’s comforting to learn that it might just be harder to locate the right kind of air filter.

  7. My son took the filter off his AC unit. Not sure why or for how long. But the land lord says it has done damage to the AC. Which froze up and thawed out and isn’t working. Is this possible. Can not using a filter harm the unit. I believe it has only been off a couple days.

    • If it’s a window AC unit you need to clean the coils in the front of the AC unit right behind the filter. Supposedly you are supposed to take out the window AC twice a year and spray coil cleaner on the inside and outside of the unit and rinse it with a water hose.

  8. I want to change my furnace filter. I can’t find any filter on my furnace. I can see an air scrubber attached to the furnace…..I really don’t know what an air scrubber is. We have looked for any kind of filter and can’t find one. This is a manufactured home. I do not know how old the furnace is. It is an Amana.

  9. I also have 2 returns(up&down stairs) but I located the spot on the handler in the attic where in a video shows where it she be but nothing? Had the original looking AC tape? Thank you for any guidance

  10. There is still a question that I have about air filter location. All I hind in my small one story house is what I guess is the return that is about 2X3 ft and tightly secured to the wall. Every other house I’ve lived in had an overhead filter. These were easy to see and change. That’s why I’m wondering if I’ve found the filter.

  11. HI I have a heat pump in my attic since my ac is working but not blowing cold air but I could not find any filter there so i could clean to get cold air please help

  12. Carrier Model153E35AXXX Serial #; 1310101165 Register No. Given when parts were sent :668 8311. We had this unit installed about 4 years ago–If you can find a filter with these numbers typed by an 80 y/o man after a glass o, I would like to commend youf wine

  13. Thanks for letting me know that there are air filters behind each return grill in your home. My husband and I have noticed that our air conditioner isn’t running as efficiently as it usually does—it hasn’t been cooling super effectively, and our energy bill has also increased quite a bit. We’re thinking that it might be due to air filters that need to be replaced, so we’ll definitely check all of those filters.

  14. Not sure if mine is a filter problem because the return filter is replaced in my hallway often. The unit is about 5 years old. We recently switched the thermostat from cooling to heat. I noticed the fan was staying on and the room temp wasn’t getting that much warmer so I checked the thermostat and saw Aux Heat instead of Heat On under the temp I set it for 72. The inside temp says 64….very chilly in here right now! I looked up what Aux Heat meant and it was a scary description due to it comes with monstrous bills! I shut the unit down and put some socks on for now. I’d rather layer up that run up a bill. Any suggestions on why it is reverting to Aux Heat or how I can stop that? I’m in Virginia and the weather is just now cooling down so no freezing outdoor temps are a factor. Thanks!

    • Hi, Lisa,
      Danny says, “It sounds like either the thermostat is failing or a relay in the heating system itself. I would suggest calling in a professional who can diagnose the problem very quickly. Good luck!”

  15. BRYANT 310AAV024070 (for heating) & BRYANT 113ANA24 13 SEER (2ton AC) was installed recently. Can’t find the air filter. Please help. Regards, Rudy

  16. First time owning a house with a gas a/c & heat pump unit. Went to change the filter, and there appear to be 2 slots, and the current filter is cross straddled between the two notches. This is an American Standard 2017 model TEM6AOC42H41SAAt with the filter slot horizontal, right under the unit. Any thoughts on which slot to slide it into?

  17. Just purchased an 8year old home, just discovered there is no filter in the AC return on the wall. And there is no framing for a filter to fit into to. I know this is not safe, what should we do?

    • Hi, Verna,
      Some A/C units have a reusable fiber filter that fits into a slot on the bottom of the air handler as opposed to the one that fits into the grill on the wall— although these work, they are not ideal as they filter less air.
      You can purchase the hinged grills that hold an air filter at The Home Depot. You’ll just need to try to match the size of the existing grill opening.
      Good luck!

  18. I just moved into a new Townhouse (brand new construction), that is a leased apartment community. I noticed there is no A/C filter in one vent return located above the inside stairs. She said the system doesn’t require one. I wasn’t able to get any more information from her. I’m quite concerned. Can I just take the vent panel off and sit a filter inside it? I haven’t been able to find any information on the internet about HVAC systems not needing a filter. Additionally, I’m a long-term cancer survivor and past history of asthma/allergies, and would like to ensure I’m doing everything to keep my household free of contaminants.

    Please advise….

  19. I just recently purchased a home 2 months ago and I can get any air flow in the master bedroom. The master is on the only room on the main level and it’s cool soon as I step out my master. I need help figuring out how to fix that problem.

  20. When I clicked on your site to learn about air filters audio started playing on how to stabilize a shelf to work on it (no thanks, I’m trying to read about air filters!) and I couldn’t find anything to pause. I know how to mute the site so it’s fine for me but other people might not know how to mute your website. I’m not sure if you have it playing on purpose or if it’s a web design error that needs to be fixed. Just bringing it to your attention in case it’s a mistake! Thanks for sharing information and have a good day!

    • Hi, Beth! Our Simple Solutions segments are so popular that we’ve made them easily accessible in the sidebars of our pages.
      The video player has a mute button and a pause button. 🙂
      Thanks for your message.

  21. On horizontal HVAC units with the return duct attached to the side of the air handler, the filter often fits in a slot on the return air side of the unit. On vertical air handlers with the return air duct entering on the top of the air handler, the filter often slides into a slot above the HVAC unit.

    • Thanks for sharing your thoughts with the Today’s Homeowner community, Joven!
      TH community members helping other TH community members — we love it. 🙂


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