Two similar blocks of flats have been built for people with respiratory diseases. The buildingshave a clean and effective ventilation system and low emitting building materials. Theventilation system is a centralized supply and exhaust air system, either based on demand(Building A) or user controlled (Building B). Total volatile organic compound (TVOC) levelsand concentrations of ammonia and formaldehyde were measured in one apartment on each ofthe six floors of both buildings before occupants moved in and after 3 and 7 months and afterone year of occupancy. The indoor air quality (IAQ) achieved the high quality target levelafter 7 months of occupancy and remained at this level during the 1-year follow-up period.