Humidity in Operating Rooms

Does the ANSE/ASHRAE/ASHE Standard #170, which reduced the minimum relative humidity requirement for operating rooms to 20%, apply to existing operating rooms as well as new operating rooms? 

20%-60% RH can be considered as an operational best practice for both new and existing ORs and other short stay patient care areas.  CMS, however, will continue to write up health care organizations during validation surveys if the 35% of NFPA 99 is not met until they have issued interim language that will permit the lower limit.  Waivers may be applied for if an OR occasionally falls below the 35% RH during this cold winter season. 

ASHRAE 170 and the Guidelines for Design and Construction for establishing relative humidity in ORs and other short stay patient care areas:

 
1)  Both ASHRAE 170 and the Guidelines are for new construction and major renovations of health care facilities.  They both reference the same table within ASHRAE 170, Table 7.1 Design Parameters.  The title is very important as it clearly emphasizes the intent - DESIGN PARAMETERS of ventilation systems.  In addendum "b" of ASHRAE 170 the committee has even made it more clear about RH% by adding "design" to the column heading for RH%. 

2)  Since neither of the two documents referenced above are intended to represent an operational standard of care, we are concerned with meeting requirements because CMS states in its interpretive guidelines: 

CMS Interpretive Guidelines §482.41(c)(4) 

Temperature, humidity and airflow in the operating rooms must be maintained within acceptable standards to inhibit bacterial growth and prevent infection, and promote patient comfort. Excessive humidity in the operating room is conducive to bacterial growth and compromises the integrity of wrapped sterile instruments and supplies. Each operating room should have separate temperature control. Acceptable standards such as from the Association of Operating Room Nurses (AORN) or the American Institute of Architects (AIA) should be incorporated into hospital policy. 

Note: 

For reference, the AIA document referenced is the Guidelines for Design and Construction of Health Care Facilities of which ASHRAE 170 is an official part of the document for 2010, including addenda, and AORN also references the Guidelines and was part of the coalition to modify the lower level humidity to 20%.  AORN is working on modifying its 2008 Perioperative Standards and Recommended Practices to reflect the acceptable range of 20% - 60%. 

3)  At this moment CMS is still working on some formal interim language that will permit this lower limit even though they reference the 1999 edition of NFPA 99 which states: 

NFPA 99 

6.4.1.1* The mechanical ventilation system supplying anesthetizing locations shall have the capability of controlling the relative humidity at a level of 35 percent or greater. 

Note: 

For reference this section of NFPA 99 is left over from the days of flammable anesthesia and is being removed from the 2012 edition of NFPA 99. And, if you read the words closely it does not state that the level needs to be maintained above 35% only that the system have the capability of controlling the RH% at a level of 35% or greater. 

4)  MOST IMPORTANT - The experts have researched and reviewed this issue for over two years and have spoken with one voice - a 20% to 60% RH in ORs will NOT create an unsafe condition, will NOT increase surgical site infections, will NOT cause patient discomfort, it WILL decrease energy, and it WILL keep those health care organizations with marginal humidification, especially during very cold winter days, from being cited by CMS. 

Note: 

The experts include: Association for Professionals in Infection Control, Centers for Disease Control and Prevention, National Institute of Health, Association of periOperative Registered Nurses, ASHRAE, and ASHE.