I bought a couple of expensive remote weather sensors because they were the only ones I could find that included sensing atmospheric pressure and wet bulb temperature along with the ordinary metrics like temperature and humidity. Though air quality and particulate count is not included, I have done without for two reasons, which is that I live in the country surrounded by water and forest and cleaner air than I have ever known, and in contrast, the small house is old, dusty, I can easily see the particulates floating in the air, and because I know it is bad, I just don't need to know any precise measurements. My only complaint concerning the devices, which seem to be rugged and accurate, though with an almost absurd accompanying price tag, is that the required app and its interface design is comically bad in every measure that could matter. If there are interested developers, please take a look at the product[1] and the software[2], and see if you're interested in developing and selling me and other customers, and perhaps even the manufacturer, an application that collects and displays data from this family of devices that doesn't completely and utterly suck.
Indoor air quality can be greatly affected by all kinds of things in your home, from the building materials to the paints, coverings, veneers, veneer glues, fabrics, etc. etc. etc.
So in other words, while your outside air may be quite good such that it doesn't negatively affect your indoor air quality, that does not at all suggest that your indoor air quality will be good.
I know, and I know it's bad in there, but knowing precisely how bad is not useful information. A week away and there's a film of dust on everything. Most places, the dust is human skin, but not here. I think it's the old veneer covering the cinderblock walls and the cinderblock. Place was built in the 1940's, and it is slowly deteriorating particle by particle. But the rent is cheap. I have a HEPA filter on a box fan for the bedroom that runs constantly, which I hope helps, and I spend my days outside.
I have a 1940s place w/o cinderblock that does this heavy dust thing too. I'm also not fantastic about making it sparkle so as a result I do get dust bunnies. I've examined a few up close, and they look like laundry lint, a generally uniform light colour and texture. It's weird, I installed the exhaust duct myself, it's sealed and directly vented to the outdoors, my furnace fan runs every 20 minutes or so and has a merv 11 filter on it I believe, so there is some minor filtration. And yet, all this dust..
My place is not at all airtight, but I am skeptical that the outdoors air has this degree of lint fibers floating around at all times.
I get what you describe, grey dust bunnies, quickly accumulating within a week after cleaning the floor under my bed. Because it is only around my bed that I see those, I assumed it was coming from my bed clothes, the blankets in particular. idk what the material is called, but generally when new it's described as "scratchy" by children, probably wool or polyester. Shaking these outside produces a lot of junk flying off. But the dust that I see accumulate elsewhere and floating through the air turns the off-white base-boards a sickly dark yellow, and the dust is black on a paper towel when wiped. Maybe wash your bed clothes and rinse thoroughly, and skip the dryer sheet. I've found too much detergent drys or sticks on clothes and produces a puff of particles when I take off my socks too quickly, in particular.
[1] https://kestrelmeters.com/products/kestrel-fire-weather-drop
[2] https://apps.apple.com/us/app/kestrel-link/id1489485544