PRACTICAL SAFETY VENTILATION IN\ua0ULTRACLEAN AIR OPERATING ROOMSWhen planning new ultraclean air operating rooms, often the first\ua0question is which is the preferred room air distribution system andwhat system is the best to meet the requirements of microbiological\ua0air cleanliness. Today, in Sweden, the requirement is a target level of5 CFU/m3during the design phase, in order to ensure that the level of\ua0≤10 CFU/m3during infection prone surgery is maintained.This study is based mainly on the analysis of published scientific\ua0reports and other documentation. The focus is to compare the mainprinciples for room air distribution systems, mixing and displacement\ua0principle and to see whether the requirements of microbiological aircleanliness can be fulfilled during ongoing surgery. Three different\ua0distribution systems available in Sweden have been compared.The room air distribution systems studied are:\ub7 Mixing airflow/partly displacement\ub7 Unidirectional airflow (UDF)\ub7 “Temperature controlled airflow (TAF)” - A specific Swedish\ua0room air distribution system.The result of the comparison shows that in operating rooms for\ua0infection prone surgery all three studied room air distribution systemscould achieve the target level of 5 CFU/m3 when the air volume flows\ua0are above 2 m3/s provided that the total microbiological sourcestrength does not exceed 10 CFU/s.The total microbiological source strength depends upon the number of\ua0people in the operating room, their chosen surgical clothing system,and their activity level.Keywords: Ultraclean operating room, room air distribution system,\ua0airborne bacteria-carrying particles, microbial source strength,\ua0surgical clothing syste
