The effects of outdoor air supply rate and supply air filter condition in classrooms on the performance of schoolwork by children (RP-1257)

Two independent field intervention experiments were carried out in mechanically ventilated classrooms receiving 100% outdoor air. Outdoor air supply rate and filter condition were manipulated to modify indoor air quality, and the performance of schoolwork was measured The conditions were established for one week at a time in a blind crossover design with repeated measures on 10- to 12-year-old children in two classes.

Seven exercises exemplifying different aspects of schoolwork (numerical or language-based) were performed as part of normal lessons by pupils who also marked visual analogue scales to indicate their environmental perceptions and the intensity of any symptoms. The children indicated that the air was fresher but otherwise perceived little difference when the outdoor air supply rate increased from 3.0 to 8.5 L/s (6.4-18 cfm) per person, while the speed at which they performed two numerical and two language-based tasks improved significantly.

A significant effect of ventilation rate was observed in 70% of all the statistical tests for an effect on work rate, but there were no significant effects on errors. The effects were probably due to improved air quality in the classrooms as judged by a sensory panel of adults blind to conditions, as perceived by children, and as indicated by the reduction in the average CO2 concentration from 1300 to 900 ppm, taking this as a marker of reduced bioeffluent concentration.

It was not possible to test the effect of replacing a soiled filter with a new one because very little dust had been retained by the "used" filter and because of an incompletely balanced design. The unbalanced design also made it impossible to test for an interaction between filter condition and ventilation rate.

These results indicate the importance of improving indoor air quality and ventilation in classrooms.