For the past few months I’ve felt phlegm and odd coughs and finally changed my filter recently and noticed there wasn’t a return/intake like most apartments.

I grabbed the model number of the unit which is: ACNF250615AB. It is a Goodman “pancake” horizontal “Air Handler” and I noticed there is this big room (crawl space) that doesn’t seem to go anywhere.

Should I be concerned? I have a new born and feel like this may be out of code unless the existing air doesn’t need to be filtered and clean air is from the outside unit? But still my other apartments had a air return unit that sucked in the and filtered with a MERV 12+ filter before pushing through the supply ducts.

Here are some photos to help investigate and clarify this for me, please and thank you!

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The opening you are seeing is a 24”x12” filter door above the restroom.

The 1st photo is a outside shot 9’ above floor. The 2nd is a closer look inside (that air goes to no where) but has return pressure. The 3rd is a under shot of the bottom of the unit with the three air supplies attached to in the 1st and 2nd photo from inside the restroom. Lastly a image of what I assume I’m missing, (which is a residential outtake) but should be an entire unit or duct attached leading to the unit at least right? Whats the purpose of filter if the intake isn’t being filtered.

*The outside vent (first photo) sucks in air, but to where and why isn’t it actually being filtered, we live in Texas, incase code criteria needs to be evaluated, but this explains why we though the filter wasn’t working.

  • Have you asked your local inspector?
    – Questor
    Mar 31, 2023 at 17:40
  • 1
    Are you assuming that a ventilation fan is required, and that's what is missing? Return through a plenum isn't unusual.
    – KMJ
    Mar 31, 2023 at 18:14

2 Answers 2


This passage is the return/intake for the system. That's why it has a filter grille and filter. Supply air always goes through ductwork, but return air is allowed to pass through building cavities without formal ductwork as shown in your picture.

The final photo shows an illustration that's applicable to a whole-house ventilation fan. You're looking at a heating and cooling system in your apartment, though, and that's an entirely different thing from whole-house ventilation.

Some HVAC systems are designed so that a portion of the return air is drawn from outdoors. We can't tell whether yours might be designed this way or not. I haven't heard of an HVAC design that would waste conditioned supply air directly to the outdoors for the benefit of ventilation.

To help identify possible causes for the health symptoms consider what else began occurring around that time. Did you move into this apartment around then, or begin using the HVAC system around then?

It's normal for an HVAC system, and especially a large air return plenum like yours, to contain some dust. In theory the system soon reaches an equilibrium in which the dust just sits there because it's too heavy to be stirred up by the amount of air that flows over. Still, you could request to have the ducts and specifically this return space cleaned -- it's possible to do, but the apartment manager may expect you to bear the cost and you'll need to recognize that the cleaning may or may not improve your health symptoms. A self-contained portable HEPA filter appliance might be a better use of the money, but again, if air quality isn't what ails you then the HEPA filter won't help.


No, the crawl space you see is full of dust and particulates from the wood and sheetrock. It is not filtered at all even if you had two MERV 13 filters - the air that enters the vent will become contaminated again because the unit you have was not installed correctly.

From the first open vent photos you posted it appears that the return doesn’t have a fitted filter on the unit itself and is not safe or recirculating the air correctly and cleanly which explains the phlegm, you may be in hailing drywall and tons of dust. The return appears to recirculate the inside air improperly.

Which almost makes the opening vent seem pointless without ductwork from the opening to the unit; you should contact you local OSHA rep, a EPA, or HVAC specialists.

  • 1
    OSHA has nothing to do with residences.
    – nobody
    Apr 5, 2023 at 0:22

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