Experiences from wall exhaust systems in blocks of flats.

A self administrated questionnaire was mailed to over 300 dwellings in blocks of flats usingthe wall exhaust. In almost all the dwellings there was a controllable ventilation unit. Theunits were either a mechanical exhaust ventilation system type with outdoor air inlets ormechanical supply and exhaust ventilation system with heat recovery and outdoor air intakeon the wall. In the questionnaire, the daily use of ventilation unit, noise levels as well as odorsand their sources in the dwellings were asked. The prevalence of odors in the dwellings usingwall exhaust was in the same level as in dwellings with traditional way to conduct exhaust airfrom dwellings to roof reported in earlier studies. Habitants in the dwellings with mechanicalsupply and exhaust ventilation system reported less draught, slightly less odor problems andjudged the air quality more fresh even in the bedrooms in the mornings than habitants indwellings with mechanical exhaust ventilation system only. Habitants in dwellings withmechanical supply and exhaust ventilation system were much more satisfied with theventilation system and, then regarded their dwellings more comfortable than habitants indwellings with mechanical exhaust ventilation only.