For the modeled indirect exposures, we note that while this was a worst-case office exposure
scenario with a low ventilation rate of 0.3 h-1, even if ventilation rates are tripled to 0.9 h-1,
which exceeds the ASHRAE 62.1 [9] default minimum ventilation of 0.78 h-1 for the modeled
office space, the indirect exposures still present a significant health risk. Ventilation rates would
have to be increased by a factor of 23 to mitigate the health risks for the 9 chemicals modeled.
Clearly ventilation is not a solution and e-cigarette use will have to be regulated indoors in the
same manner that is done for tobacco smoking, which is prohibited indoors in many countries,
including the US.