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

Abstract

background: In exposure studies and risk assessments, the intake of a pollutant through inhalation is often estimated using the well mixed concentration in the room. More advanced ventilation systems such as stratum ventilation, displacement ventilation or personal ventilation systems aim at higher ventilation efficiencies by creating flow conditions that divert from the well mixed condition. In these cases, as well as in the assessment of exposure to pollutants with near field sources such as text markers, glue, detergents etc. the validity of the use of the well mixed concentration will be limited. To improve understanding of intake in such conditions, the fate of pollutants near the breathing zone needs to be studied closer. aims: The aim of this paper is to determine the geometrical extend of the inhalation zone of standing, sitting and sleeping persons by determining the inhaled fraction of a near field source of a gaseous pollutant and to determine a geometrical zone around the nose where the full mass of the emitted pollutant is inhaled. methods: In this paper, we present the results of experiments with a breathing thermal manikin in an environmental chamber using SF6 as a tracer for gaseous pollutants. results: The thermal plume that is generated by the metabolic heat output has a large impact on the shape of the inhalation zone, limiting exposure to near field sources to those situated almost directly under the nose and next to the torso. For the sleeping manikin, 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. conclusions: Based on these results, we conclude that the inhalation of near field sources is dramatically underestimated by the use of the well mixed concentration, especially for sources located on the upper torso, neck and chin of the exposed person.