In this study we evaluated the diffusion of nitrous oxide in a few operating rooms, using spatial data modelling techniques, in order to assess hospital staff exposure and to promote risk management. Indoor air sampling was carried out, during routine operating activity, by means of transportable infrared spectrometer, with geostatistical techniques. We detected high average concentrations of nitrous oxide (from 8 ppm to 445 ppm, with a peak of 1345 ppm). Linear geostatistical iso-value maps of the anaesthetic gas expected values showed an evident nitrous oxide-rising trend near the anaesthetic machines, near walls and doors, near HVAC opening, etc. Operators' attention to maintenance procedures of the anaesthetic machines, and to hazard management of the operating room, can reduce health risks of the hospital staff exposed. To conclude, we have to underline that an assessment performed only on "mean" samples and calculated through descriptive statistics, would not allow any inferences in the complex spatial structure and physical kinetics evidenced by geostatistical methods.