Fig. 1

Upper panel: Weekly mean (± s.e.m.) numbers of cigarettes smoked/day and ENDS uses/day. Lower panel: Exhaled CO readings (mean ± s.e.m.) at each session
Upper panel: Weekly mean (± s.e.m.) numbers of cigarettes smoked/day and ENDS uses/day. Lower panel: Exhaled CO readings (mean ± s.e.m.) at each session