I’ve spent a good amount of time in this space, mostly WRT cleaning air in wood shops. One of the problems is that the 12% difference there is mostly the smalle

I’ve spent a good amount of time in this space, mostly WRT cleaning air in wood shops. One of the problems is that the 12% difference there is mostly the smallest particles, and those are the most harmful. It’s hugely noticeable with smoke, for instance. Humans don’t have a great sense of smell, but we do very well with smoke. The difference between air with <1% leftover smoke and air with 13% leftover smoke is obvious to everyone. The EPA has a lot to say about this, if you’ve the patience to wade through it — https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-...