Development of an optical, real time measurement method for Air Change Rates in indoor areas

This paper describes the goals and results and discusses the requirements and marginal conditions for an optical measurement method that is currently being developed in a publicly funded research project. This method is based on measuring the light intensity of a laser beam absorbed by fog particles by using simple components such as a laser pointer and a webcam. The fog (e.g. commercially available disco fog) is uniformly distributed in the room to be examined. The concentration of the fog is reduced by the natural decay of the particles, mainly by the air conditioning system with fog-free outside air. The laser beam is positioned in the room so that it sufficiently represents the test area. The air change rate (ACR) can be determined by the increase in laser light intensity over time detected by the camera.