Operating Room Humidity Requirements

Updated July 19, 2017

Operating rooms are required to deploy desiccant dehumidification units in an effort to regulate relative humidity. Low humidity can cause electrostatic charges and patient hypothermia. High humidity causes increased growth of bacteria and fungus as well as uncomfortable conditions for the operating room staff. Keeping the relative humidity at 50 per cent eliminates unfavourable conditions in the surgical suite.

Electrostatic Charges

Low levels of relative humidity cause an increase in electrostatic charges. These charges are electric currents between two objects and may cause damage to electrical equipment. In the presence of oxygen gas, a spark can cause a fire or explosion. Operating rooms must be kept at a relative humidity of 50 per cent to eliminate these risks.

Patient Hypothermia

Patients are susceptible to hypothermia, or abnormally low body temperature, during lengthy surgical procedures where humidity is lower than 35 per cent. Relative humidity set at 50 per cent reduces the chance of both hypothermia and the drying of mucous membranes.

Airborne Bacteria and Fungus

A relative humidity of 50 per cent controls the growth of airborne bacteria, thus minimising infections in operating room procedures. In addition, the dry air from desiccant systems eliminates mould and mildew growing in air ducts and filters.


Heat from lights and equipment, multilayered gowning and lengthy surgical procedures cause surgeons and operating personnel to perspire. Desiccant dehumidification units that keep relative humidity at 50 per cent ensure comfort and reduce the incidence of stress-induced errors.

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About the Author

Margi Desmond has been writing since 1993. She attended East Carolina University and worked as a journalist for "The East Carolinian" and "The Marauder." She has written presentations, newsletters and manuals for financial, insurance, health care and automotive industries. She earned a Bachelor of Science in communications.