The importance of controlling temperature and humidity in surgical areas has been well documented over the years by various organizations such as ASHRAE, the American Society for Health Care Engineering (ASHE), the Association of periOperative Registered Nurses and the Association for the Advancement of Medical Instrumentation, to name a few. 

Currently, ASHRAE/ASHE Standard 170-2017, Ventilation of Health Care Facilities, defines the minimum relative humidity (RH) level for an operating room as 20% and the maximum level as 60%. While published guidelines are applicable to all facilities, each facility must contend with variables such as geographic location/climate variations and the type, age and condition of HVAC systems supporting these surgical areas. 

Hospitals located in arid regions of the country, or that have variable seasons, may find it difficult to maintain RH levels between 20% and 60% during certain periods of the year. Additional factors such as storage of sterile supplies and the possible impact on medical equipment used in the operating rooms also must be considered. 

Developing a staff response plan when temperatures or humidity levels are out of range is crucial to controlling the risk of health care-associated infection as well as maintaining staff comfort. This can be done by using a multidisciplinary team approach and should include representation from perioperative services, infection control, engineering, sterile processing and risk management. Conducting a risk analysis to determine the impact on patient safety as well as services and supplies when temperatures or humidity levels fall out of the acceptable range in surgical suites will greatly aid in developing an appropriate staff response plan. 

The risk analysis and response plan should also factor in variables such as the degree of temperature and/or humidity deviation, the severity and consistency of the deviation, the duration of out-of-range status and the time period (e.g., occupied versus unoccupied) in which the deviation occurs. 

Lastly, effective monitoring of space temperature and humidity, which can be accomplished either manually at frequencies determined by hospital policy or through the use of a building automation system, are both vital to understanding trends and should also be considered when developing the response plan. 

To better understand how temperature and RH affect one another, visit the link in the box to the left to watch a video on the topic.