Stymne H, Hansson P, Boman C A
Bibliographic info:
21st AIVC Conference "Innovations in Ventilation Technology,", Hague, Netherlands, 26-29 September 2000

A number of single tracer gas techniques (decay, step-up, homogeneous constant emission,inlet pulse and homogeneous pulse) suitable for measuring the local mean ages of air in multizonebuildings exist, each having their advantages and drawbacks. The characteristics of thedifferent available techniques are compared from theoretical and practical points of view. Thehomogeneous pulse technique has not been experimentally validated before. This techniquerelies on pulses of tracer gas being injected into the different zones in amounts, which areproportional to the zone volumes. Some advantages with the "homogeneous pulse" technique,compared with the "inlet pulse" technique, are that the pulses can be injected at any time path,that they must not necessarily be short and that the evaluation of local mean ages of airinvolves a simple total time integration of concentration, making it possible to utiliseintegrating air samplers (e. g. adsorption tubes).The homogeneous pulse technique is tested against the decay technique in a five-room indoortest house, using both automatic and manual injection of tracer gas. It is shown that thistechnique yields results as accurate as the decay technique. Using manual injection (withsyringe), however, requires special caution in order to achieve a uniform distribution of theinjection in a room and to avoid redistribution while walking between rooms.