Utvärdering av avklingnings- och homogenspridningsmetoden vid jämförelse mellan deplacerande, omblandande och utjämnande ventilation

Sammanfattning: People spend a lot of time indoors, closer to 90% of their lifetime. To obtain a good indoor climate with good air quality buildings need to be ventilated. Therefore, they are often equipped with mechanical ventilation systems. Nevertheless, SBS (Sick Building Syndrome) is a serious problem. The reason that some buildings become "sick" is believed to be due to, among other things, poor ventilation. To determine if a ventilation system is good or bad, several measures of the ventilation system can be determined. It can be made by many methods, eg. tracer gas methods as the decay method and the homogeneous emission method. The aim of this study was to calculate various measures of the functions of the ventilation systems, with the aim to determine whether the results can be related to how the air movements actually looked like and if the methods' results were reliable when nitrous oxide was used as a tracer-gas. To determine the air movements, tests with smoke were also performed. A secondary objective of the study was to compare the different ventilation systems, with the aim to determine which yielded the best results. This work was conducted on AirSon Engineering AB's headquarters in Angelholm. Measurements were carried out in a test room which would be compared to a normal office. With each method tests were made on a mixing, a displacement and leveling ventilation system. Measurement methods yielded low results for both the air exchange efficiency and the ventilation efficiency. But the movement of air in the test room was poor and the results were therefore considered to be correct. With the homogenous emission method, too few results were obtained to make a fair assessment of the reliability of the method, regarding air exchange efficiency. However, the reliability of local ventilation index calculations was considered to be good. With the decay method, all results could be related to how it actually looked in the room and the method was therefore considered to provide reliable results with nitrous oxide as a tracer.