ISO EPM1 60 % Grade Type Filter (F7) Behavior in a Building with Air Recirculation

Mechanically ventilated buildings use filtration to remove particles from supply air. In cases without recirculation, the concentration of particles in the supply air is simply the outdoor concentration multiplied by the filter penetration. However, some building ventilation systems partially recirculate exhaust air to reduce energy consumption and, to some extent, lessen particle loading on the filters. Under these circumstances the indoor air concentration is more difficult to estimate. Here, we present a case study from measurements in an office building, where the average recirculation ratio (the portion of recirculated exhaust air of the total supply air) was measured as 0.65. The single-pass efficiency of the filter is compared to the apparent particle penetration when air is recirculated, showing a benefit of air recirculation...