Beyond standardized chamber testing: Effects of spatial placement and ventilation on portable air cleaner performance in a large test room

Standardized tests for portable air cleaners (PACs) typically evaluate devices in small, well-mixed chambers with central placement and no interaction with mechanical ventilation (MV), diverging significantly from real-world operation. This study bridges this gap by systematically evaluating PAC performance under more realistic, yet controlled, conditions in a large test room (202.0 m³) where mixing fans are switched off during measurement, allowing non-ideal mixing conditions to develop, and where MV interaction is explicitly accounted for. Three representative PAC types, horizontal front discharge (Type I), vertical upward discharge (Type II), and horizontal table-mounted discharge (Type III), are evaluated at up to six positions in PAC-only and combined PAC+MV (ACH = 3 h⁻¹) scenarios across four particle size ranges (PM 0.25 , PM 0.25–0.5 , PM 0.5–3 , and PM 3–10 ). Placement sensitivity is strongly particle-size dependent: fine particle CADR pr differences are typically within 15% (S = 5–19%), while coarse particles show variations up to 46% (e.g., the upward-discharge PAC at low fan speed with MV, +887 m³/h relative to central placement). Central placement, commonly recommended in standards, is not universally optimal, consistently underperforming for Type II and showing position-dependent performance for Type I and III. PAC–MV interaction is generally near-additive for both fine and coarse particles; meaningful super- or sub-additive effects are limited to selected coarse-particle cases, where the interaction factor exceeds the uncertainty threshold (±0.16). Spatial spread analysis reveals that high average air cleaning performance can coincide with highly uneven room coverage, highlighting that CADR pr alone is insufficient to assess overall effectiveness.