Practical Safety Ventilation in Ultraclean Air Operating Rooms

Licentiate thesis, 2018

PRACTICAL SAFETY VENTILATION IN ULTRACLEAN AIR OPERATING ROOMS

When planning new ultraclean air operating rooms, often the first question is which is the preferred room air distribution system and

what system is the best to meet the requirements of microbiological air cleanliness. Today, in Sweden, the requirement is a target level of

5 CFU/m3during the design phase, in order to ensure that the level of ≤10 CFU/m3during infection prone surgery is maintained.

This study is based mainly on the analysis of published scientific reports and other documentation. The focus is to compare the main

principles for room air distribution systems, mixing and displacement principle and to see whether the requirements of microbiological air

cleanliness can be fulfilled during ongoing surgery. Three different distribution systems available in Sweden have been compared.


The room air distribution systems studied are:

· Mixing airflow/partly displacement

· Unidirectional airflow (UDF)

· “Temperature controlled airflow (TAF)” - A specific Swedish room air distribution system.


The result of the comparison shows that in operating rooms for infection prone surgery all three studied room air distribution systems

could achieve the target level of 5 CFU/m3 when the air volume flows are above 2 m3/s provided that the total microbiological source

strength does not exceed 10 CFU/s.


The total microbiological source strength depends upon the number of people in the operating room, their chosen surgical clothing system,

and their activity level.


Keywords: Ultraclean operating room, room air distribution system, airborne bacteria-carrying particles, microbial source strength, surgical clothing system