Acetylene in breath: background levels and real-time elimination kinetics after smoking.

We have measured the acetylene concentration in the exhaled breath of 40 volunteers (31 non-smokers, nine smokers) using near-infrared cavity ring-down spectroscopy. The acetylene levels were found to be the same as in ambient air for non-smokers, whereas elevated levels were observed for smokers. Real-time measurements with sub-second time resolution have been applied to measure the elimination kinetics of acetylene in breath after exposure to tobacco smoke. Three exponential time constants can be distinguished from the data and these can be used to define the residence times for different compartments, according to the multi-compartment model of the human body.