Table 5. Carbon monoxide in parts per million (ppm) in the exhaled air at 12-month follow-up, n = 99.

CO concentration*	Self-reported smokers	Self-reported non-smokers†	n (%)
⩾7 ppm	65 (80.2%)	2 (11.1%)	67 (67.7%)
0–6.5 ppm	16 (19.8%)	16 (88.9%)	32 (32.3%)
n (%)	81 (100%)	18 (100%)	99 (100%)

*Measured with a NeoMed EC50 CO analyser (see Methods); †7-day abstinence.