Impact of Ventilation Air Supply Type on Indoor/Outdoor PM

In-Situ Measurements

Abstract

Indoor comfort has been given significant attention to satisfy the occupants’ needs, yet the Covid-19 pandemic accelerated awareness for creating also a healthy atmosphere. Besides infectious aerosols, Particulate Matter (PM) and Volatile Organic Compounds (VOCs) can induce health issues on the short and long term. Commercial ventilation systems are increasingly based on providing a good indoor comfort by monitoring CO2, RH, and/or VOCs while targeting a low as possible energy consumption. Indoor PM is determined by various indoor and outdoor sources ranging from cooking and household activities to outdoor PM transported or infiltrating into the building. Consequently, the indoor PM level varies and potentially affects human health. This research contains in-situ measurements with Renson Senses quantifying indoor and outdoor PM in and near one single dwelling for examining the impact of commercial ventilation systems (Mechanical Extract Ventilation (MEV) and Mechanical Ventilation with Heat Recovery (MVHR)) on indoor PM1, 2.5, 4 and 10. The measurements encompassed four system configurations either without filter (natural or mechanical supply) or mechanical supply equipped with ISO Coarse >90% or ISO ePM1 50% filters to assess the filter efficiency in practice. The extraction flow rate was kept constant and identical to avoid the impact of different air exchange rates on indoor PM. Each configuration was active during two weeks resulting in a two months period (May-June, 2021) during which occupancy and indoor polluting activities were rare, allowing to assess the ventilation and filter impact on indoor PM. The analysis revealed that indoor PM levels are about half the outdoor PM levels without filtering on the air supply, when there was no occupation or activities. Using an ISO Coarse >90% filter showed no clear effect with a similar performance as an MEV system. Next to this, a MVHR system equipped with an ISO ePM1 50% filter significantly impacts the transport of outdoor PM to indoors, with an efficiency, expressed as the Indoor/Outdoor ratio, of about half the laboratory efficiency. Supposing that PM originates 50/50 from indoors and outdoors, the actual fine filter efficiency influencing indoor PM is about 15-25% of the measured lab efficiency.