Zoned exponential, vertical and horizontal ultra-clean laminar airflows: No differences in bacteriological efficiency

A Review of Air Distribution Patterns in Surgery Rooms Under Infection Control Focus

“…It is observed that for both systems, the colony forming units decrease with the increase in the number of changes of air per hour (NRC, 1999). As reported by some authors (Howorth, 1993, Friberg, 1998, systems with the diffuser centralized in the roof with exponential flow protected by air curtains are an interesting alternative. According to the authors, the exponential airflow pattern supplies a central descending flow in conjunction with a radial flow outside of the area of microbiological clean air and due to the radial outlying flow, the velocities down and outside are enough to prevent any pollutant from rising from the floor.…”

“…Although the systems with panels have been well succeeded regarding the microbiological air control (Friberg et al, 1998;Howorth, 1993), they impose a considerable restriction to the movements of surgeons, the other members of the surgical team and also to the positioning of instruments inside the surgical room. To avoid this kind of problems, systems with protection panels located approximately 2 m above the floor (Fig.…”

“…On the other hand, regarding the systems with air curtains that provide high velocity air supply in their entire periphery, tests accomplished with this type of systems show a good microbiological control (Lidwell et al 1987;Belkin, 1998;Friberg, 1998). Besides, in the systems with protected flow, the velocity of air discharge can be smaller than that found for systems without protection, since air is to be unloaded 2 m from the floor.…”

“…As some authors (Whyte, 1988;Lidwell et al, 1987;Lidwell, 1988;Belkin, 1998;Friberg, 1998;NRC, 1999) point out, the system with horizontal laminar airflow does not have a lot of applications in surgical rooms due to its high degree of contamination compared to systems with vertical laminar airflow (air supply at the roof). Figure 9 presents results obtained in a work developed by The National Resource Center -NRC, which compares systems with horizontal and vertical airflow in terms of colony forming units (CFU/ft 3 ) in function of the number of changes of air.…”

“…The control of airborne particles, chemical and radioactive dangerous substances, odor, virus and microorganisms carried by the air, is considered essential for the protection of occupants of the surgical room (Lidwell et al, 1987;Belkin, 1998;Friberg et al, 1998). To ensure accurate control of the environmental conditions and to guarantee dilution and removal of those agents, some requirements should be considered, such as: restriction of air movement within and among sections, specific needs of ventilation and filter, and temperature and humidity control (ASHRAE, 2001).…”