Recirculation of air in dwellings. Differences in concentration between rooms in dwellings due to the ventilation system.

The Dutch Standard NEN 1087 "Ventilation of dwellings": Requirements (1) is at this moment under review. A requirement can be found about the quality of air. In fact a statement is made that outside air is required as fresh air for bedrooms. Bathroom, kitchen, W.C. and living-room are allowed to be ventilated with air from other rooms. During the last years air heating systems became more popular. These systems have,in its most simple form,recirculation of air from the living-room to the bedrooms.