Biological monitoring usually relies on the collection of blood and urine samples. Although being non-invasive
and providing an inextinguishable sampling pool, the analysis of exhaled breath is not well established. A gas phase
measurement is, however, inherently simpler than the analysis of complex biological fluids, and modern methods have
identified hundreds of volatile compounds in the breath of persons exposed to normal environmental concentrations. The
most commonly deployed analytical techniques in breath analysis are gas chromatography combined with mass spectrometry
(GC/MS) and other MS-based methods. Lately, also laser-based optical methods, such as cavity ring-down spectroscopy
(CRDS), have emerged in the field. With such instruments, it is possible to accurately quantify the concentrations
of volatiles in exhaled breath down to below part-per-billion (ppb) levels with sub-second time resolution. Laser
spectroscopy thereby enables real-time investigations during and after exposure to exogenous chemicals. In general, depending
on the sampling approach used, the measured levels of the breath compounds may vary significantly. It is therefore
of importance to systematically study and account for the phenomena affecting the recorded concentrations, and subsequently
select an appropriate sampling and measurement strategy. In Helsinki, we have used CRDS to study the background
levels of hydrogen cyanide (HCN), ammonia (NH3) and acetylene (C2H2) in the exhaled breath of healthy volunteers.
Different sampling techniques have been employed in an effort to standardize the breath sampling event. The realtime
elimination kinetics of breath C2H2 after smoking has also been studied.