I appreciate this. I used to row competitively through high school and college, so I do consider myself an "athlete" as an identity, but non-practicing. I recently lost 30 lbs (6'0" from 200lbs to 170 lbs) over the past year through diet, but need to exercise.

Your advice for air filters is good general advice, IMO. I have a 700 sqft apartment with:

1x Honeywell HPA300 (rated for 465 sqft)

6x Coway AP-1512HH (each rated for 361 sqft)

1x Honeywell HPA100 (rated for 155 sqft)

I also have a Honeywell FPR 10 filter on the HVAC air return. So, over 2800 sqft of CADR-rated filtering for a 700 sqft apartment. Activated carbon pre-filters are changed every 2 weeks and the HEPA filter is changed once a month. We spend about $400/mo on filters, on top of $1,100/month rent.

Unfortunately, HEPA filtration does little for the type of air contamination that we're dealing with. Ethylene oxide is more like a "VOC" than a "PM2.5". The activated carbon filters help a bit, but are "used up" very quickly (1-2 days IME). The HEPA filters do very little/nothing for VOC contamination as far as we can tell.

Indeed, it is time to move away. I am in one of the most heavily-affected featured areas in this article[0]. However, my wife and I work in the chemicals industry, so we have personal experience identifying most of the compounds by smell and have unusual awareness of their effects vs. most of the nearby citizens.

0: https://www.propublica.org/article/toxmap-poison-in-the-air