Experimental assessment of the inhalation zone of standing, sitting and sleeping persons

Abstract

In exposure studies and risk assessments, the intake of a pollutant through inhalation is often estimated using the well mixed concentration in the room. Less traditional ventilation systems such as stratum ventilation, displacement ventilation or personal ventilation systems aim to achieve higher ventilation effectiveness by delivering supply air directly in the occupants' vicinity, thus creating flow conditions that divert from the well mixed condition. Also, with sources in the near proximity of occupants, the concentration in the occupants breathing zone is often much higher than the one predicted assuming well mixed conditions, and assessment of exposure often requires calculation of pollutant concentrations in the inhalation zone. In this paper, we present the results of experiments with a breathing thermal manikin in an environmental chamber that define the geometrical extend of the inhalation zone of standing, sitting and sleeping persons breathing through the nose. These results allow to determine the inhaled fraction of a near field source of a gaseous pollutant and determine a geometrical zone around the nose where the intake fraction is equal to 1 as a reference for the selection of sampling positions in exposure studies. The experiments show that a person's thermal plume has a large impact on the shape of the inhalation zone, limiting the inhalation zone of standing and sitting persons to the area situated almost directly under the nose. For a sleeping person, the breathing zone is stretched down along the cheeks due to this same effect. The transient effect of the breathing cycle has only a minor influence on the inhalation zone.