Fine dust measurement in ducts of balanced ventilation systems

The measurement of particulate matter (PM) in rooms has gained interest in the last decade. However, the sensors that are currently used are intended for use in still standing air and cannot be applied to ventilation ducts with a typical velocity up to a couple of meters per second. Therefore, a prototype of a measurement module for particulate matter has been developed for use in ducts of ventilation systems. To the author’s knowledge, this has not been done before.
The PM2.5 values as measured by the prototype in an extract duct, were compared with the values as measured in the room where the air is extracted from. The differences between the measured PM2.5 values were 2 to 4%, which was a sufficient accuracy for the prototype.
Three field tests were carried out in three houses with a balanced ventilation system in The Netherlands, with a distance between the houses of 50 km up to 150 km. For each field test, two PM measurement modules were installed near the balanced ventilation unit; one in the extract duct and one in the supply duct. During the measured period in the heating season, the heat recovery ensured similar temperatures in the extract and supply ducts, resulting in PM2.5 values that could easily be compared with each other.
The measured PM2.5 values in the extract ducts showed typical indoor PM sources like cooking, but also showering and steam ironing because water droplets are also measured by the sensor. In the supply air, peaks caused by incidental recirculation of chimney smoke into the fresh air intake were visible. Moreover, the effect of filter type (fine or coarse) and of filter age (old or new) within the ventilation unit could be found.