OBJECTIVE Isoflurane is a suitable agent to produce sedation in the intensive care unit (ICU). However, data concerning occupational exposure to isoflurane during long-term sedation are not yet available. The purpose of this study was to evaluate occupational exposure to isoflurane in the ICU. METHODS Trace concentrations of isoflurane were measured directly by means of photoacustic infrared spectrometry during isoflurane sedation in ten cases over a period of 24 hours. Values were obtained at four personnel-related and two leakage-related locations in an ICU chamber. RESULTS All measured values were low, the majority under 3 ppm isoflurane at the personnel-related points. Peak concentrations up to 40 ppm were recorded for several minutes during nursing interventions. At measurement point "nearby patient's mouth" values up to 5 ppm were recorded, at location "anaesthesia machine" values ranged from 2 to 69 ppm isoflurane. CONCLUSIONS We conclude that an effective high flow scavenging system, a low-leakage anaesthesia machine and an airconditioning equipment without recirculation could keep occupational exposure low. The majority of the measured values was below the NIOSH recommendation (2 ppm). All values was lower than a national state recommendation (10 ppm). Under other circumstances (e.g. without scavenging system) air pollution will be higher and therefore measurements at the working place are needed.