My local school system hired a contractor over the summer to improve the HVAC and also fix all the windows such that they can open if they were previously broken and stuck closed. I don’t specifically know if they “got it right” but I’m not sure why you’re so skeptical … measuring air changes per hour, installing HEPA filters, etc. … that’s standard stuff in the same category as following electrical code, designing buildings with proper structural support, etc., I think, and I expect whatever overpriced building firm they hired did it correctly … (This is in a medium-sized town in the USA.)
My local school system hired a contractor over the summer to improve the HVAC and also fix all the windows such that they can open if they were previously broken and stuck closed. I don’t specifically know if they “got it right” but I’m not sure why you’re so skeptical … measuring air changes per hour, installing HEPA filters, etc. … that’s standard stuff in the same category as following electrical code, designing buildings with proper structural support, etc., I think, and I expect whatever overpriced building firm they hired did it correctly … (This is in a medium-sized town in the USA.)