Occupational exposure to hazardous airborne pollutants: effects of air mixing and source location.

The presence of airborne pollutants in indoor environments has been associated with occupants' discomfort and/or adverse health effects. This study investigates occupational exposure in relation to indoor air mixing and source location relative to a human body. Experimental and computational methods were used to provide information about the pollutant distribution in the vicinity of the human body for different levels of room air mixing. Study results show that the often used assumption of uniform pollutant distribution in an occupied space is not always appropriate for estimation of inhalation exposure. Results also indicate that an occupant may experience very high acute exposure to airborne pollutants when little air mixing exists in a space and the pollutant source is in the vicinity of the occupant. The buoyancy-driven flow induced by the convective heat transfer from an occupant's body can transport pollutants in the occupant's vicinity to the breathing zone. Specific study results reveal that a source located in the occupant's front chest region makes a relatively large contribution to the breathing zone concentration compared with the other sources in the vicinity of the human body. With the source position in this region, exposure can be nine times greater than that calculated with the uniform mixing assumption. The buoyancy-driven convective plume around a body seems to have a significant influence on pollutant transport and human exposure, especially in the absence of room air mixing.