Box fans with filters are cheap and foolproof and BIFL or close to it, but if you want something prettier I’ve had good luck with the BlueAir from Costco. Dead simple and effective in bedrooms.
https://en.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box
https://www.costco.com/blue-pure-mini-max-air-purifier%2C-2-pack-by-blueair.product.4000339230.html
I second the Blueair purifiers. I have the 211+ non auto in my living room and the smaller versions in my bedrooms. I've had the 211+ running for about ten years and still going strong. The smaller ones I had to replace recently. I got the table top Mini Max through Costco in a 2-pack and I regret that size. I'll get the smaller standing 411 ones again next time.
We have Blue Air - a large one in the main living area, which catches kitchen/cooking particulate, and a mini one in each kid room. Costco has two packs of the minis for $99 right now!
This particular model is designed for a 100 sq ft room. You would probably need to run both purifiers on the highest setting all the time to cover even a small 400 sq ft studio, and that would be kinda noisy. These are not designed to clean an entire apartment, just a single room.
You can put them in a single room and close the doors and windows to that room to get the best filtration possible. Just make sure you still have a little ventilation (like a ceiling vent or leaving the door cracked open a bit) if you're planning to do it for a long period of time so that you don't get too much CO2 buildup.
If you are cleaning the air with the purpose of removing pollen, close your windows. If you were running them to clean viruses out of the air, then leaving the windows open would improve ventilation, so that would actually help. However, if you are running them to help with allergies or wildfire smoke, then keep the dirty air outside so they can do their job on the air that's inside.
According to BlueAir's marketing, their HEPASilent filter is supposedly even better than a HEPA filter. I'm no expert but in my experience they work at least as well as HEPA filters. I like them because they're quiet, cute, and effective. I can see all the junk in the air that got trapped in the filter when it's time to change the filter out.
If you want to run just one machine on a quiet setting, then look for one that is rated for the size of your apartment.
For whatever it is worth, purchased this two pack for $100 from Costco “blue pure mini max” to put in our less inhabited rooms of the home. We have coway in primary living spaces.
https://www.costco.com/Blue%20Pure%20Mini%20Max%20Air%20Purifier,%202-pack%20By%20Blueair.product.1896710.html?COSTID=iosapp_25.8.2&TRACKING=NO&adobe_mc=TS%3D1755361137%7CMCMID%3D47448641111624073557868459186739136500%7CMCORGID%3D97B21CFE5329614E0A490D45@AdobeOrg&sh=true&nf=true
theflintseeker
