Air purifiers reduced indoor PM2.5 from 18.0 to 3.7 μg/m³

In a randomized, single-blind crossover trial in a mixed-mode ventilated Beijing office, sixty employees worked under two conditions: desk air purifiers switched off (control) and switched on (intervention), placed at their breathing zone. Average indoor PM2.5 measured 18.0 μg/m³ in the control condition and 3.7 μg/m³ during the intervention, and this contrast was then used to compare cognitive test performance between conditions.

For those managing office environments, this points to desk-level filtration as a workable way to lower personal PM2.5 exposure during working hours, even where whole-building ventilation is mixed-mode and harder to control. The study links this reduction to better performance on several cognitive skills, particularly memory, suggesting indoor air quality at the individual workstation can bear on daily cognitive function, not just long-term respiratory health.

The evidence here is well supported for the exposure measurement itself: PM2.5 levels were directly monitored in both conditions of a controlled crossover design. It applies to one urban office setting in Beijing with sixty participants and short-term exposure; whether the same reduction would occur, or matter cognitively, in other climates, ventilation systems or exposure durations is not established by this design.