Blocking cigarette filter vents with lips more than doubles carbon monoxide intake from ultra-low tar cigarettes

Light and ultra-light cigarettes achieve their lower tar, nicotine, and carbon monoxide (CO) yields on smoking machines largely by means of air-dilution vents on the filters. Previous research showed that blocking 0%, 50%, and 100% of the filter vents on a 1 mg tar cigarette with tape directly increased expired air CO levels. The present experiment extended this research by replicating the 0% blocked and 100% blocked conditions with the addition of a condition in which participants (N = 12) were asked to block vents with their lips. Mean CO boosts for the unblocked, lip-blocked, and tape-blocked conditions were 2.7 ppm (SE = 0.52), 6.7 ppm (SE = 1.0), and 12.9 ppm (SE = 2.2), respectively. Analyses suggested that lip blockade effectively blocked approximately 50% of the filter vents. Subjective ratings of cigarette strength, harshness, and heat increased significantly as degree of vent blocking increased. Cigarette smokers need to be warned about the presence of vents and the consequences of vent blocking.