Technical performance and perceived feasibility of mobile air cleaning devices in classrooms: A pilot study

During respiratory virus outbreaks, mobile air cleaning devices (MACs) are increasingly considered in schools as a preventive measure. However, evidence on their real-world performance, feasibility, and potential health impact in classroom settings remains limited. This pilot study was conducted to inform the design of a future large-scale trial by providing a comprehensive evaluation of MACs in primary school classrooms, integrating technical performance (including indoor air quality and airborne microbial assessments), user-perceived feasibility, and the suitability of illness-related absenteeism as a potential pragmatic outcome measure for infection rates. A randomized cross-over study was conducted in five Dutch primary schools, involving 45 classrooms equipped with MACs. Each classroom alternated between three-week periods with the devices switched on and off. Indoor air quality was assessed in a subset of classrooms using sensors for CO₂ and particulate matter, while airborne microbial contamination was monitored through air dust sampling and molecular testing. Illness-related absenteeism was evaluated as a potential outcome measure. MACs effectively halved indoor particulate matter levels, confirming their technical performance. This reduction did not translate into a measurable reduction in airborne microbial contamination, although such contamination was successfully detected. Feasibility assessment revealed low acceptability among teachers due to reduced environmental comfort. Absenteeism was identified as a suitable proxy for infectious diseases, with simulations indicating that a future cluster-randomized trial would require 40-70 schools to detect a 20-25% reduction in absenteeism.