The influence of human activity on the vertical distribution of airborne particle concentration in confined environments: preliminary results.

Vertical concentration profiles for various size fractions of airborne particulate matter have been measured in a nonsmoking indoor environment used mainly as a meeting point during coffee break (11.00 a.m.) and tea time (4.00 p.m.). This monitoring exercise was carried out using a novel sampling system specifically designed for measuring concentration gradients of airborne particles (but which can be easily modified for gaseous pollutants) over the first three metres from ground. The results show substantial gradients in concentration, with the highest occurring at around 1.3 m height. A plausible explanation for the measured time series of concentration at different levels from ground, and the vertical distribution of concentration, is thought to be human movement and activity in the confined environment. The implications that the results of this experiment have for indoor air quality standards for airborne particulate matter are discussed.