Figure 2 summarizes the results of complete design analyses that examine the effects of operating electrostatic air cleaners on how pupils performed the tasks presented to them during the experiments.
When electrostatic air cleaners were in operation in Experiment 1EF, pupils reported the classroom to be warmer (P<0.001) and more noisy (P<0.006) and the air to be drier (P<0.028).
The assessments of air quality in classrooms without pupils in experiment 1EF indicate that when the electrostatic air cleaners were in operation, the acceptability of classroom air quality tended to improve (P<0.07) and the air was perceived as significantly less stuffy (P<0.009).
The present results show that the operation of electrostatic air cleaners substantially reduced airborne particle concentrations in all size ranges and in all five schools, as intended.
The operation of electrostatic air cleaners in some cases had significant positive effects and in others had significant negative effects, and the effects are too numerous to have occurred by chance alone.
Operation of effective electrostatic air cleaners would certainly be expected to provide some health benefits in the long term, especially for allergic or asthmatic children, but in the present study in which the length of intervention was only one week it does not appear to have provided any short-term benefits as found in the study in London offices by Wyon et al.
In the present experiments, electrostatic air cleaners were operated in classrooms and significantly reduced the concentration of airborne particles by at least the amount in previous experiments, but no effects on the performance of schoolwork were observed.