For those concerned about shooting indoors, I guess it depends on the range.
I only shoot indoors and weekly if I'm able. Certainly bi-monthly at worst. And that's since my sons flew the coop in 2013. So over 10 years.
I shoot at NRA HQ and they've advertised for years the quality of the HVAC/filtration. I used to shoot at a range also touting its HVAC. Unfortunately for the shooting public, last spring it was purchased by the county police department for their training facility.
I am very concerned with NRA's predicted move to Texas. The only remaining range within reasonably close distance and cost is sketchy.
But anyway, again, it depends.