Methods The FRESH study (Forced-ventilation Related Environmental School Health) was designed to investigate the effect of a CO 2 controlled mechanical ventilation intervention on classroom CO 2 levels using a longitudinal cross-over design. Rock File Manager Pro Ota Download. Target CO 2 concentrations were 800 and 1200 parts per million (ppm), respectively. The study included 18 classrooms from 17 schools from the north-eastern part of The Netherlands, 12 experimental classrooms and 6 control classrooms. Data on indoor levels of CO 2, temperature and relative humidity were collected during three consecutive weeks per school during the heating seasons of 2010–2012. Associations between the intervention and weekly average indoor CO 2 levels, classroom temperature and relative humidity were assessed by means of mixed models with random school-effects. Background Children spend much of their time in schools; it is the indoor environment where they spend most of their time besides in their home. It is therefore important that schools have a good indoor air quality (IAQ).

Classroom ventilation was already recognised as an important determinant of indoor air quality in the beginning of the 20 th century []; however, even recent studies showed that classroom ventilation rates do not meet building standards. Two studies performed in The Netherlands in 2007 showed that more than 80% of the schools exceeded CO 2 levels of 1200 parts per million (ppm) during classroom occupation [,], which in The Netherlands is the advised maximum CO 2 concentration for classrooms [,].