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Video camera calibrations and field tests for air change rates in a test house were performed to develop a new method of measuring air change rates using a video imaging technique. From the camera calibrations, it was found that good correlation was achieved between image signals and luminous reflectance of achromatic color chips by appropriately adjusting the pedestal level of the video camera so that the image signals were made equal to zero for the black level of the picture. In the field tests, air change rates in the test house were measured from the decay curves of video image signals obtained by the step down method, assuming a perfect mixing of smoke particles inside the spaces. With the proposed video method, it was possible to measure air change rates with virtually the same precision as derived from the decay curves of smoke particle numbers using an aerosol monitor. As a new tracer, smoke liquid mists without dirty residuals were also tested and compared to the gas method using SF6 . It was thus verified that the video method using smoke liquid mists could also precisely measure air change rates with an error of less than 6% in comparison with the gas method.

Units: SI

Citation: ASHRAE Transactions, vol. 105, pt. 1