Combining air filtration with ultra-fine particle sensing for an enhanced energy-efficient indoor air quality optimization

A satisfactory indoor air quality (IAQ) relies, amongst other things, on the availability of clean ventilation air. The outdoor air cleanliness in many urban environments is far from optimum. Fine particles (FPs = 2.5 m) and certainly ultra-fine particles (UFPs = 0.3 m) feature prominently as hazardous constituents of common urban air pollution. Installed filters in ventilation units of buildings and cars can clean mechanically supplied ventilation air.However, because affordable particle sensors of sufficient reliability and robustness are notcommercially available, the degree to which the applied ventilation and filtration strategy is able to control the absolute indoor pollution level at any time remains usually unknown. This paper introduces a UFP sensor capable of recording the ambient UFP pollution level, yielding a sensor signal that relates to the relative inhalation-induced health hazard of airborne UFPs.The monitoring functionality of this sensor can be used for creating awareness with regard to the ambient UFP pollution level. For control purposes, UFP sensors can be used in addition to common T, RH and CO2 sensors. Furthermore, a new type of electrostatically-enhanced particle filter is presented that accomplishes its air cleaning functionality in a more energyefficient way than a comparable mechanical filter. Providing air handling units with particle filters as well as with UFP sensors downstream of these filters and/or in indoor spaces allows for a versatile control of air handling units that explicitly takes the indoor UFP pollution level into account as a decision factor for the ventilation strategy. This enables an enhanced sensorcontrolled fine-tuning of the IAQ with anticipated savings in power consumption.