Does Indoor Air Quality actually make a difference, or is it overhyped?

Improving indoor air quality with portable HEPA filtration has a real but genuinely inconsistent randomized-trial evidence base, with cardiovascular benefits appearing in some trials and not others. Weighing the data: Indoor Air Quality looks an early-stage, lower-priority area for now — the evidence is only moderate (45/100), and its estimated impact (28/100) is on the lower end too.