Regarding to HVAC in hospitals, what is the recommended ACH in the operating rooms?

Dear all

As i know for the Operating room the ACH for outdoor air is15 where recirculation is not allowed

where re circulation is allowed outdoor ACH is5 and recirculation is20 -25

Hope this will work

20 ACH

Surgical-site infection is the leading complication of surgery. Normal skin flora of patients or healthcare workers causes more than half all infections following clean surgery, but the importance of airborne bacteria in this setting remains controversial. Modern operating theatres have conventional plenum ventilation with filtered air where particles >/=5 microm are removed. For orthopaedic and other implant surgery, laminar-flow systems are used with high-efficiency particulate air (HEPA) filters where particles >/=0.3 microm are removed. The use of ultra-clean air has been shown to reduce infection rates significantly in orthopaedic implant surgery. Few countries have set bacterial threshold limits for conventionally ventilated operating rooms, although most recommend20 air changes per hour to obtain50-150 colony forming units/m(3) of air. There are no standardized methods for bacterial air sampling or its frequency. With the use of HEPA filters in operating theatre ventilation, there is a tendency to apply cleanroom technology standards used in industry for hospitals. These are based on measuring the presence of particles of varying sizes and numbers, and are better suited than bacterial sampling. Environmental bacterial sampling in operating theatres should be limited to investigation of epidemics, validation of protocols, or changes made in materials which could influence the microbial content.

According to ASHRAE2011 the conditions are as following:

+ve pressure

min. outdoor ACH4

min. total ACH20

R/H =30 ~60 %

temp. =68 ~75 F

ACH20 is the normal practice for hospitals as per ASHRAE guidelines.