What is the typical relative humidity range maintained in the operating room?

• A. 5-10 percent
• B. 50-70 percent
• C. 70-85 percent
• D. 20-60 percent

Answer: (D)

Maintaining moderate relative humidity in the operating room helps control several factors that impact safety and performance. A typical target is about 20-60 percent relative humidity. This range reduces static electricity so instruments and drapes don’t spark, helps keep staff and patient mucous membranes comfortable, and limits condensation on surfaces and equipment. It also keeps microbial growth in check more than in very humid environments. If humidity is too low, static discharge, skin and airway irritation, and excessive dust can be problems. If humidity is too high, condensation on cold surfaces and increased risk of microbial growth and equipment corrosion can occur. Therefore, the range around 20-60 percent is preferred. The option with 5-10 percent is far too dry, 50-70 percent is higher than the ideal ceiling, and 70-85 percent is too humid for an OR.