Temperature, Humidity, and Airflow in Your ASC Operating Rooms
By: Rommie Johnson, MPH, PMP
Program Director
Posted: May 20, 2025
Maintaining optimal temperature, humidity, and airflow in your ambulatory surgery center’s operating rooms isn’t just about comfort; it’s a critical measure to prevent infections, safeguard sterile fields, and ensure that equipment functions properly.
ACHC Standard 15.01.02
ACHC Standard 15.01.02 stipulates that OR settings comply with American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) requirements for healthcare facilities. The parameters defined by ASHRAE focus on reducing infection risks and ensuring equipment reliability.
Standard 15.01.02 requires attention to:
1. Temperature: Keep temperatures within ASHRAE guidelines to support patient comfort, maintain safe equipment operation, and inhibit bacterial growth.
2. Humidity: Maintain between 30% and 60% humidity to prevent excessive moisture. Moisture can damage equipment and promote microbial growth and overly dry conditions, which can in turn impact sterile supplies. Reducing humidity below 30% requires adherence to manufacturer’s specifications and CMS waiver protocols.
3. Air pressure relationships: Ensure air pressure remains positive to keep contaminants from entering sterile fields.
4. Monitoring and documentation: Log readings for temperature, humidity, and airflow at least once daily for every OR in use. Readings outside of defined limits must trigger immediate corrective action to restore safe and compliant conditions.
Challenges and Solutions for Compliance
Practical application of these environmental controls in ASCs can prove complicated, with the standard being noted as deficient on more than one quarter of accreditation surveys.
Consider the following strategies to address your ASC’s challenges:
Challenge: Limited on-site control over HVAC settings
Facilities that rely on external building departments for HVAC adjustments face delayed responses, which often affect facilities’ ability to make immediate corrections. This can lead to prolonged non-compliance when busy surgical schedules demand immediate control..
Solution: Integrate real-time environmental monitoring
Installing monitoring sensors in each OR enables an ASC to detect and respond immediately to deviations in temperature, humidity, or airflow. Connecting sensors to a centralized alert system can notify staff when environmental conditions fall outside the required range, allowing for prompt calls for adjustment before procedures are affected.
Solution: Empower staff to make environmental adjustments
ASCs that rely on external building services may consider training key personnel to make minor HVAC adjustments when conditions require immediate attention. Empowering staff to control the surgical environment improves response times and minimizes disruptions, particularly when external teams cannot respond quickly.
Challenge: Uncontrolled humidity levels
High humidity may link to the challenge noted above: limited direct control over HVAC adjustments. In one ASC, humidity reached 72% during a procedure, requiring hours of intervention from the building’s facility team before returning to acceptable levels. Such deviations jeopardize equipment and patient safety.
Solution: Establish protocols for immediate corrective action
Guide staff to act when environmental conditions deviate from acceptable ranges. For example, if humidity levels are approaching 60%, protocols could require staff to notify leadership, document the event, and suspend procedures, if necessary, until conditions are stabilized. Clear, predefined steps reduce uncertainty and help ensure rapid and consistent responses.
Solution: Conduct routine HVAC inspections
Regular inspection and maintenance of HVAC systems can help ASCs avoid unexpected failures or prolonged deviations from required levels in the OR environment. Inspection and maintenance should target critical aspects of the HVAC system, such as filters, ventilation, and pressure regulators.
Challenge: Inconsistent airflow monitoring and inadequate documentation
Facilities often struggle to maintain consistent logs for temperature, humidity, and airflow. Missing or incomplete data not only weakens the facility’s compliance standing but also limits its ability to respond proactively to environmental changes. When reversed airflows or pressure imbalances are missed, sterile fields can be compromised, increasing the risk of surgical site infections (SSIs).
Solution: Maintain a daily log
Each day your OR is in use, staff should take measurements of the room environment and log readings. The record produced from these readings provides clear evidence of compliance and offers valuable insights into potential safety issues. (See also the “Integrate real-time environmental monitoring” solution listed above.)
An Environmentally Controlled OR Is a Safe OR
Maintaining environmental standards is an ongoing effort that demonstrates commitment to a safe surgical space. Environmental awareness encourages staff to prioritize compliance, understand the impact of environmental conditions, and actively monitor for deviations.
Frequent team check-ins to review recent environmental logs and discuss any deviations can reinforce the importance of compliance and create an open dialogue about challenges. By engaging staff in these discussions, leadership promotes a collaborative approach to environmental safety.
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Read more articles about Ambulatory Surgery Center Accreditation here.