Operating Room Humidity Levels

High quality ventilation is an essential part of a patient's well-being. Health care facilities, especially operating rooms, require proper ventilation to lessen the risk of infection simply by breathing air-transmitted pathogens.

Authoritative Body

• The American Society for Heathcare Engineering (ASHE) and the American Society of Heating, Refrigeration, and Air (ASHRAE) released a manual in 2008, outlining the design requirements to ensure high-quality ventilation. ASHE/ASHRAE standard 170-2008 was the first in the nation to specifically target ventilation requirements for heath care facilities.

Humidity Effects

• To lessen the risk of surgical site infections, environmental conditions in the operating room must be controlled. Humidity and temperature are two of a multitude of factors involved in the spread of infectious diseases. Humidity also causes condensation to form on the ceiling, eye glasses and microscope lenses. This was the driving force for change.

Humidity Standards

• In June 2010, ASHRAE Standard 170 Standing Committee changed the requirements for relative humidity levels in the operating rooms to 20 percent. Previous temperature and humidity levels were determined by each surgical team's preferences and ranged from 30 percent to 72 percent.

Oversight and Maintenance

• Operating room humidity levels are controlled by the plant operations manager and his staff. The appointees are hospital maintenance engineers with heating ventilating and air conditioning (HVAC) certification.

Design Information

• The humidity levels are now controlled by adding a desiccant dehumidification unit to pre-condition ventilation air prior to mixing it to the return air from the operating room. Furthermore, cooling coils are integrated into the system prior to the desiccant unit to assist in the removal of moisture and lower the dew point.