Aorn Humidity Guidelines [updated] Jun 2026

| Issue | Potential Cause | Action | | :--- | :--- | :--- | | | HVAC humidifier malfunction; Outside air is extremely dry (winter). | Activate humidification systems; Check for leaks in the room envelope. | | Humidity too high (>60%) | HVAC chiller failure; Moisture intrusion; Too many people in the room. | Check air handler status; Reduce room occupancy if possible; Verify supply air temperature. | | Fluctuating Readings | Sensor calibration error. | Recalibrate sensors; Replace sensors if readings drift consistently. |

In a dry environment (below 20% RH), static electricity builds up rapidly. In an OR where oxygen, alcohol-based prep agents, and electrosurgical devices are present, a static spark can trigger a surgical fire. Maintaining >20% humidity allows static charges to dissipate naturally. aorn humidity guidelines

Historically, the standard for OR humidity was much higher (30%–60%). However, based on updated research regarding bacterial growth and equipment tolerance, AORN guidelines now align with the current trend in standards: | Issue | Potential Cause | Action |

Note: Check your facility’s policy – some state health departments or accreditors (e.g., TJC, DNV) may still require 30–60% or 35–60%. In such cases, the stricter standard applies. | Check air handler status; Reduce room occupancy

Here are the humidity guidelines for operating rooms (ORs), based on the latest recommended practices.