Relative Humidity - Requirements

What are relative humidity requirements for critical spaces?

Any examples are for illustrative purposes only. 

The Joint Commission expects organizations to have a process in place to demonstrate that proper relative humidity (RH) levels are maintained in all critical areas. 

New facilities are to comply with NFPA 99-2012 that includes ASHRAE Standard 170-2008, Ventilation for Health Care Facilities.  Existing facilities are to be maintained as originally designed and installed at the time of construction. 

In April 2013, CMS issued a categorical waiver in its Survey and Certification (S&C) letter 13-25-LSC & ASC that allowed for the lower limit to be reduced 20% RH for anesthetizing locations. Organizations electing to use the lower RH, must first ensure that sterile supplies and equipment used in the operating room are safe to store and can operate at this lower RH.  A risk assessment is required using evidence-based guidelines, including the manufacturers' instructions for use (IFUs) to confirm that the supplies and devices in these locations are not adversely impacted.

Additional Resources:
EC.02.05.01/EP 15: Hospital, Critical Access Hospital
EC.02.05.01/EP 7: Ambulatory, Nursing Care Center, Office Based Surgery
NFPA 99-2012: 9.3.1
ASHRAE 170-2008
Click here for further information on waiver and equivalency requests
Last updated on March 19, 2021
Manual: Hospital and Hospital Clinics
Chapter: Environment of Care EC

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