Three curves are presented that predict how populations of (1) nonsmokers, (2) mixed smokers-nonsmokers, and (3) smokers would rate the comfort quality of ventilating air, within an enclosure, as a function of tobacco smoke content. Forty-one data points, many previously unpublished, determine these curves. Earlier publications, having only 10 of these same points available, made considerably different predictions. Curves are also included predicting the percent of occupants who will find any given tobacco smoke content acceptable.