A recent investigation into the thermal environment of tropical housing required a low cost method for the measurement of high ventilation rates. As a result a simple measurement system, using the detection of the decay of smoke density, was developed. The sensor, based on an infrared LED emitter and a silicon diode receiver, was easily portable, highly robust and could be constructed for less than 50. It was found to be suitable for the measurement of decay rates in excess of 20 air changes per hour.
A study of the reliability of systems by considering the ability of different systems to maintain a required air flow rate over time is included in a subtask of IEA Annex 27 "Evaluation and Demonstration of Domestic Ventilation Systems". Measurements were performed to determine the variation in ventilation rates due to variation in climate and variation in performance of the ventilation system. The monitoring was carried out in one-family houses and apartment buildings, which are representative of the Swedish housing stock.