FIGURE 2.

Exhaled carbon monoxide (eCO) [parts per million (p.p.m.)], electronic cigarettes (EC) versus EC + combustible cigarettes (CC). (1) Values are absolute at 1 month; no significant between‐group differences at baseline. (2) Values are absolute at 8 months (1 and 4 months also available); no significant between‐group differences at baseline. EC + CC group also had significantly reduced CC consumption [from 23 cigarettes per day (CPD) to five CPD]. All groups had notably low CO at baseline. (3) Change data at 4 weeks