A new technique for measuring air change rates in indoor spaces using the step down method of video image signals

通过摄像机校准、风洞实验和现场实验，开发了一种利用视频成像技术测量空气变化率的新方法。相机标定表明，图像信号与消色差彩色芯片的发光反射率具有良好的相关性。这是通过适当调整摄像机的底座水平来实现的，这样图像信号在图像的黑色水平上等于零。在风洞实验中，采用降压法获得的空气假设示踪雾在空间内完美混合。视频图像法测量空气变化速率的误差小于高速碳氢化合物分析仪示踪气体法的9%。在现场试验中，还使用烟雾蜡烛作为示踪剂测量了具有试验空间的试验室内的空气变化率。实验证明，视频法测量空气变化速率的精度与使用气溶胶监测仪测量烟雾颗粒浓度衰减曲线的精度几乎相同。

Video camera calibrations, wind tunnel experiments and field experiments have been performed to develop a new method of measuring air change rates using a video imaging technique. The camera calibrations showed good correlation between image signals and luminous reflectance of achromatic color chips. This was achieved 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 wind tunnel experiments, air obtained by the step down method assuming perfect mixing of tracer mists inside the spaces. The video image method could measure air change rates with an error of less than 9% of those by the tracer gas procedure using a high-speed hydrocarbon analyzer. In the field tests, air change rates in the test house with test space were also measured using smoke candles as tracers. It was verified that the video method could measure air change rates with virtually the same precision as derived from the decay curves of smoke particle concentrations using an aerosol monitor.