Like many people in Hong Kong, I eat out about four times a week, meet friends in bars and occasionally visit a nightclub. And last week, I passively puffed on three cigarettes, thanks in

part to a lack of smoking restrictions in bars, clubs and restaurants.

Using a commercially available piCO Smokerlyzer, I measured the level of carbon monoxide in my lungs after nights out over the course of two weeks.

The device measures the levels of carbon monoxide in exhaled breath in parts per million (ppm) and, although it is not a scientific measure of passive smoking, it gives an indication of the presence of the gas that makes up about 20 per cent of cigarette smoke.

Before each evening out, I spent 40 minutes on a treadmill, enabling me to calibrate the meter to zero.

I chose bars and restaurants close to the gym so as to avoid contamination from vehicle fumes.

The results were surprising. Three hours in fairly open bars and restaurants gave me a reading of between 2ppm and 4ppm, while the evening spent in the music club registered an eight.

A reading of 10ppm is equivalent to smoking one cigarette. This means I have been 'smoking' three cigarettes a week for the past 10 years in Hong Kong. A non-smoking catering worker will 'smoke' approximately 12 cigarettes over the course of a week.

Anthony Hedley, chair professor of community medicine at the University of Hong Kong, says: 'There is no way I'd [go to a smoky bar]. I'm 65 and taking extreme care to avoid that kind of environment because there would be a measurable change in the function and behaviour of [the] arteries with that kind of exposure.

'If you go on doing that year in, year out, there will be measurable changes. How much and how fast

that progresses through repeated exposure would depend on an individual's susceptibility.'