Or indoors, for that matter. It's very easy for a house to reach 50 to 100 on an AQM meter, which isn't going to be immediately noticeable, but which very well

Or indoors, for that matter. It's very easy for a house to reach 50 to 100 on an AQM meter, which isn't going to be immediately noticeable, but which very well could have long-term consequences. A good HEPA filter will take care of that. As a bonus, if you're allergic, you'll get rid of most of the pollen that way.