Human Perception of Odors and Odor Blockers

The experimental treatments include controls (clean air, irrelevant odor), blocking odors, cigarette smoke odor, and cigarette smoke odor mixed with blocking odors or irrelevant odor. To obtain cigarette smoke odor a 1 inch length of a 1R6F research cigarette is burned to completion in a sealed 5 gallon chamber fitted with septa. Using a syringe fit with a needle and filter, 60 mL aliquots of smoke odor are obtained. These smoke odor aliquots, along with blocking odors, are injected into odor sample bags fit with a septum and a valve that can be attached to the CPAP nose mask worn by each participating smoker. Participants open the valve, inhale once through the nose, close the valve, and then remove the bag from the mask before reporting odor pleasantness and the desire to smoke. A 4 min wait period is enforced between each odor presentation to prevent odor adaptation and to allow acute motivational effects to subside. During these intervals, a nature documentary was available for viewing. Two measures of the desire to smoke are made. An objective method uses a validated relative reinforcing measure, requiring participants to record how many cigarettes they would purchase at each step along a logarithmically increasing price scale that ranges from $0 to $1,120 per cigarette. The breakpoint on this scale at which a participant is no longer willing to pay is the measure of the urge to smoke. As a subjective measure, participants report their urge to smoke as a value between 0 and 100. Participants also provide a forced choice measure of odor pleasantness, indicating either pleasant or unpleasant for each odor.

In a testing session a participant sniffs a mixture of blocking odors mixed with cigarette smoke, along with control odor samples. Presentation order is randomized. Each participant is assigned their own CPAP nose mask, and masks are disinfected after use. Participants also provide demographic (age, sex, ethnic and racial background) and smoking history information (cigarettes per day, preferred brand, age at onset, and time since last cigarette).