Study on Measurement Techniques of Air Change Rates in a House Using Video Images Masaaki OHBA Air change rates in a house were measured from decay curves of video image signals assuming that pollutant gas could be completely diffused inside a house immediately after the emission of tracer gas. The experiments were conducted using both wind tunnel and actual house. From the wind tunnel experiments,it was found that if the wind speed of oncoming flow were less than 1 m/s,the results of air

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... rates measured by video images could have good agreements with those derived from decay curves of gas concentrations that were measured by the high-speed hydrocarbon analyzer. For the field tests in a house with shed-roof, the tracer was emitted by smoke tubes, and the decay of particle concentrations were measured by four sets of aerosol monitors. It was achieved that the video image techniques could prove the validity of being capable of measuring air change rates with almost same precious accuracy as the aerosol monitors.