Ozone removal by occupants in a classroom

Ozone concentrations were measured in a classroom with and without occupants, with the purpose to quantify effects on indoor 03 concentrations. The teacher and 24 11-year old pupils each removed 03 at a rate, first order in O-3, corresponding to a rate constant of (2.5 +/- 0.6) x 10(-5) s(-1) in the present locality and to a deposition velocity of 0.45 cm s(-1). The O-3-removal caused by the occupants was approximately 2.6 times larger than that of the available surfaces belonging to the classroom and its furniture. Observation of 6-methyl-5-hepten-2-one and 4-oxopentanal at maximum concentrations of 0.2 ppb and 0.7 ppb, respectively, suggested squalene from human skin oil as a reactive, ozone-consuming substance. There are indications of a source of 4-oxopentanal in the classroom, even some time after the pupils left for the day. The work presented is important for a proper description of indoor exposure, both to ozone itself and some of its reaction products when trying to quantify relations between exposure and health effects. (C) 2013 Elsevier Ltd. All rights reserved.