How big a room can a smart air purifier actually handle?

Manufacturer coverage claims (often based on a single air change per hour) are typically two to three times more generous than what reviewers recommend for allergy or smoke relief. As a rule of thumb from the specialist communities we read, divide the stated coverage by two to three for a realistic 'good' room size, or look for AHAM-Verifide ratings, which use stricter four-air-changes-per-hour math.