The scope of the method is to determine the room-average age of air in a ventilated space. To obtain the room-average age of air in the room it is only necessary to carry out measurements in the extract ducts. The theoretical background of the method is described in Reference .
By knowing the mean-age of the air in the room we can:
a) Determine the time it takes, on an average, to replace (exchange) the air present in the room.
b) Determine if the ventilated space is well ventilated or if there are stagnant zones. The method, however, does not reveal where the stagnant zones are located. To locate the stagnant zones it is necessary to monitor the local meanage of the air at several points in the ventilated space. This is described in NORDTEST method NT VVS 019.
c) Determine the room-average concenration from a dynamically passive contaminant (= follows the air motions) generated at each point in the room with the same and constant release rate.