Outside air sampling was performed above roof exhausts and at distances 20,
40, 80 and 140 m downwind from these exhausts at a height of 1.5 m. Sampling
time was set on 5 min. Data of the Dutch Meteorological Institute was used to
determine wind speed and temperature. Control sampling was performed at an
upwind point 20 m distant from the nearest exhaust to exclude any other sources
of airborne C. difficile.