FIGURE 1.

Exhaled carbon monoxide (eCO) [parts per million (p.p.m.)], electronic cigarettes (EC) versus combustible cigarettes (CC). (1) Absolute at 1 month; no significant differences at baseline. CC = those in EC condition who used CC only at follow‐up (FU) [control group of CC only mean 16.4; standard deviation (SD) = 0.7]. (2) Values are absolute at 12 weeks; no significant between‐group differences at baseline. (3) Values are absolute at 8 months (1 and 4 months also available); no significant between‐group differences at baseline. CC group also significantly reduced CC consumption [from 27 cigarettes per day (CPD) to eight CPD]. All groups had notably low CO at baseline