Inhalation intake fraction of pollutants from episodic indoor emissions

The intake fraction is the attributable pollutant mass inhaled by an exposed population per unit mass released from a source. In this paper, mathematical models are combined with empirical data to explore how intake fraction varies with governing parameters for episodic indoor pollutant releases, such as those from cleaning, cooking, or smoking. Broadly, the intake fraction depends on building-related factors (e.g., ventilation rate), occupant factors (e.g., occupancy), and pollutant dynamic factors (e.g., sorption). In the simple case of the episodic release of a nonreactive pollutant into a well-mixed indoor space with steady occupancy and constant ventilation and breathing rates, the intake fraction is the ratio of the occupants’ volumetric breathing rate to the building's ventilation flow rate. Factors such as incomplete mixing, time-varying occupancy, and sorptive interactions modify this basic relationship.