I wanted to share something I discovered that might be relevant if you don't have central air about CO2 levels indoors.
I use a guest bedroom as my home office, which is about 68 square feet excluding closet. I noticed significant improvements in my sinus after running a small HEPA filter in the room. I also have a large one in the master bedroom.
Despite the ultra-clean air, my wife sometimes complained that the rooms felt stuffy. I decided to buy a CO2 + humidity meter and was surprised at how quickly the CO2 levels rose. Within just 30 minutes, the levels were above 1000 ppm, which is where some people begin to notice effects (though I don't). After three hours, the levels were near the top of the meter's range. Outdoors levels (on Earth) are now around 420 PPM and indoors typically hover around 600-700.
CO2 meter and PM 2.5 - 0.3 meter
In the bedroom, the situation was similar. Despite the pristine air, with two people in the room, the CO2 levels were high by morning, even though the room is much larger. Humidity also up from around 54 percent.
To solve this, I installed a few quite PC fans to blow under the doors (Alexa controlled) to exchange the air with the rest of the house, but not so much that the air filter couldn't keep up. After a month of this setup, I feel noticeably better and have much less need for coffee first thing in the morning to jumpstart my brain. I feel in a better mood?
One more thing to optimise unless you live in the countryside and can open windows or have central air that brings in outdoor, not just recycles.
