Do you have a townhouse that has stairs out front, an entry on the second level, and a basement? If so, check the room in the basement behind the outdoor stairs. We had hidden mold in the room because our townhouse was built without a proper moisture shield between the brick and the drywall. This apparently was very common for brick townhouses built in the 1990s and 2000s. It got into our HVAC system and has caused many health problems.

Dehumidifier.

Sounds mostly mental on your part, so work on that. Perhaps there is something you don't like, and are projecting that onto the "air" or something of the sort?

Since you admit to being an anxious person, it's likely all that.

look into more natural materials. So many rugs are made of polypropolene ("high traffic", "washable", "indoor/outdoor" are the friendly adjectives that describe those). I have one in my house but trying to limit those.

When checking your air filters, make sure they aren’t too restrictive. Some filters can cause decreased air flow. If you don’t have pets or allergies, use the minimum merv filter suggested.

- Get vents cleaned (including dryer vents)
- Get your carpets replaced or cleaned.
- Replace or wash the blinds and curtains.
- Get attic checked for soiled(rat poop) or wet insulation and change that.
- Get a UV light put in your HVAC system where the air exchange happens.
- Change the air-filters
- Make sure that your air is venting well (attic vents). You can get a solar vent put.
- Get better windows. Or get existing windows repaired and cleaned.
- Put a layer of cheese cloth inside all the vents to catch dust.
- Dust your home well.
- Air your house well after a rain.

PS - your dogs hair and dander is possibly the problem. Make sure that you are running air purifiers every where, don't let your dog sleep with you or sit on the furniture, make sure that they are getting groomed often.

Humidity?

We’re in a weird time of year where it’s not always warm enough for AC to run and dehumidify your house. Plus, you live in a TH which can be tricky for HVAC as the multiple levels can be hard if there is only one indoor unit for the whole house.

I’ll preface this by saying that I am a very anxious person / my spouse does not think this ‘issue’ is actually an issue. That being said…

We purchased our townhome last fall. Over the past several months, I’ve felt that the air in our living room seems ‘thick’: my lungs feel kind of congested and I cough after sitting in this room. I’ve been feeling tired / not 100%. It seems to resolve after I leave the area. I’m not allergic to dogs, but we did get a second dog around the time these issues started.

We did a mold test that yielded nothing, but are having drywall repaired next week and will be able to further investigate if that is mold. Going to buy an air quality device that tests for moisture and CO2.

Anything else I should be doing?