smoke odor, like functions A and B, would be independent of the size of the space or of air space per occupant. In this respect, tobacco smoke odor behaves as a simple contaminant and ventilation requirements for reducing tobacco smoke odor should depend strictly on rate of smoking.

Twenty years after his study on occupancy odor, Yaglou (1955) reported a small experiment on tobacco smoke odor. Studying the very high smoking rate of 24 cigarettes per hour generated by six of nine occupants in his 1,410-cubic-foot chamber, he reported the need for 40 cfm (cubic feet per minute) per smoker, or 600 cubic feet per cigarette, in order to achieve moderate, acceptable odor. At about the same time, Kerka and Humphreys (1956), using similar psychophysical techniques, estimated the requirement at 2,250 cubic feet per cigarette, or 300 cfm per smoker smoking 8 cigarettes per hour. At a smoking rate of 2 cigarettes per hour, this would be 75 cfm per smoker.

Recent results have estimated ventilation needs closer to those of Kerka and Humphreys (1956) than those of Yaglou (1955), but have also uncovered limitations on ventilation as a solution to the odor problems produced by ETS. Figure 10–2 shows how tobacco smoke odor varied over time for three smoking rates and various ventilation rates (Cain et al., 1983). The line connecting the open squares in the left panel depicts the level of odor generated by nonsmoking occupancy with low ventilation. It shows that even in the presence of higher ventilation rates, smoking generated more odor than simple occupancy.

The psychophysical judges in the experiment, a mixed group of smokers and nonsmokers, assessed acceptability in addition to perceived intensity. Figure 10–3 shows the percent of dissatisfaction as a function of ventilation rate per cigarette. The ventilation rate that would lead to 20% of judges dissatisfied is 4,240 cubic feet per cigarette (shown by the vertical dashed line). Twenty percent dissatisfied is the maximum level allowed by recommendation of the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE, 1981). On the realistic assumption that the percentage of people actually smoking in a space at any given time will equal about 10%, ventilation rate per person (smokers and nonsmokers) would need to be 53 cfm (see Figure 10–3) to reduce odors to a level that would satisfy 80% of the judges.

Despite ASHRAE’s goal of satisfying at least 80% of visitors to a space, none of its recommendations for ventilation are as high



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