FIGURE 3.

Exhaled carbon monoxide (eCO) [parts per million (p.p.m.)], electronic cigarettes (EC) + combustible cigarettes (CC) versus CC. (1) Values are absolute at 1 month; no significant between‐group 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 8 months (1 and 4 months also available); no significant between‐group differences at baseline. Both groups significantly reduced CC consumption (EC + CC from 23 CPD to five CPD; CC from 27 CPD to eight CPD). All groups had notably low CO at baseline