Indirect (Passive) Exposure Assessment. We modeled exposures for a small office space (i.e.,
20.9 m2, 2.4 m ceiling), with a low outdoor air ventilation rate of 0.3 h-1 (e.g. openable window
space with no mechanical ventilation and all windows closed, outdoor air infiltration only). We
assumed continuous occupancy for 8-hours by two occupants; one e-cigarette user (125 puffs in
8 hours, 70 ml/puff) and one non-user. For this assessment we assumed that 100% of the inhaled
vapor by the user was exhaled into the indoor air and the respiratory absorption by occupants of
the exhaled aerosol in the indoor air was 100% for all compounds. We assumed a zero exposure
when away from work. This indoor exposure assessment was selected to represent a worst-case
exposure scenario.