Variation in the levels of volatile trace gases within three hospital environments: implications for clinical breath testing.

Selected ion flow tube mass spectrometry, SIFT-MS, has been used to determine the levels of volatile trace gases in the room air of three clinical environments within a busy teaching hospital. The main aims of this study were to establish background levels of trace gases and to compare them to levels typically found within exhaled breath. Over a period of one month, room air samples were collected daily from an outpatient clinic, a hospital ward and an operating theatre, in either the morning or the evening. The concentrations of seven volatile compounds were compared between different locations and different times of the day. Having established the baseline levels for these compounds, breath was collected from healthy volunteers working within each of the three clinical locations. The concentrations of isoprene, acetone, hydrogen cyanide and ammonia within room air samples collected from at least one of the three clinical environments were less than 25% of levels typically found in human breath. Based on the recommendation of previous authors these compounds may therefore be suitable for use as exhaled markers of disease. In comparison high levels of ethanol, propanol and acetic acid within room air samples collected from each location may diminish confidence in their use as breath biomarkers.