Environmental Conditions for Operating Rooms

One of the many challenges involved in completing a successful operating room project is maintaining environmental conditions which meet the demands of the surgical staff and comply with the applicable healthcare requirements. An important step in designing an operating room is to solicit input from the surgeons and surgical staff early in the design process regarding the targeted space temperature and relative humidity conditions. If this input occurs late in the design process, it could lead to major redesign of the HVAC system(s) which could lead to project delays and budget overruns.

ASHRAE Standard 170-2008, Ventilation of Healthcare Facilities, which is included as part of the 2010 FGI Guidelines for Design and Construction of Healthcare Facilities, defines the acceptable limits for operating rooms as 68°F to 75°F space temperature and 30% to 60% relative humidity (RH). Addendum d to ASHRAE 170, issued in July 2010, revised the acceptable lower limit of relative humidity to 20%. This lower relative humidity limit has recently been accepted by the Centers for Medicare and Medicaid Services (CMS) through a categorical waiver. Facilities who desire to use the 20% lower limit are required to have documentation stating this fact.

It is important to remember the correlation between space temperature and relative humidity.  As the temperature of a room is lowered, the coinciding RH level increases.  This relationship is particularly important in a surgical environment where room space temperatures are targeted to be lower than the 68°F limit identified in ASHRAE Standard 170-2008.  It is not uncommon, for example, for surgeons to request room temperatures in the range of 60°-65° F in their operating rooms.  Maintaining space RH conditions below the 60% upper limit at these space temperatures requires special consideration for the HVAC system.  Typical HVAC systems cannot adequately dehumidify the supply air during spring and summer operation to meet low space temperature and RH targets.  In order to consistently maintain operating rooms below 68°F, HVAC design solutions may require special applications including desiccant wheels or low temperature chilled water systems.

Whether you are planning major operating room renovations or a new operating room suite, it is important to work with the design team and surgical staff to define the target operating room environmental conditions in the early stages of the design process. After the desired environmental conditions are identified, the design team can evaluate what HVAC systems will be appropriate or necessary to obtain the targeted space conditions.

For questions relating to operating room design and HVAC requirements please do not hesitate to contact Duane Markey, PE at 717-845-7654 or dam@ba-inc.com.

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