Few areas in a hospital have more critical control needs then those where surgical procedures occur. These areas have exact requirements for temperature, humidity, pressurization, and ventilation. The drivers for these conditions are literally “life and death” and are critical for both infection control as well as for the condition of the patient and the effectiveness of the operating room staff. 

By necessity, these critical areas are energy intensive. In fact, they are arguably the most energy-intense spaces in a health care facility. But that doesn’t mean that they can’t readily be controlled in a method that is safe, productive, and efficient. 

Let’s start by looking at the basic parameters of control for a surgical or procedure area.


In general, the temperature for operating rooms is the same as for other areas of a hospital — in the range of 68?F to 75?F. But it is not unusual to find surgical teams that like to have the ability to have a colder operating room. Maintaining lower temperatures, and still holding humidity levels, is a challenge that generally requires specialized systems and control design. 


While control of temperature is primarily a comfort issue, control of high humidity is important for infection control. Historically, the recommended levels were in the range of 30% to 60% although this has recently been revised to allow usage down to as low as 20%. Reducing the lower level of humidity control can provide savings, but that decision requires careful evaluation.

Air movement.  

Air movement requirements vary, ranging from 15 to 25 (or higher) ACH. Consider these ventilation levels when setting up the airflow distribution, which will often require the use of systems with reheat.

Fresh air.  

Most standards require about 20% outdoor air for operating rooms, but some hospitals prefer to have 100% OA.

Space pressurization.  

For infection control, keep operating rooms at a net positive pressure in relation to adjacent spaces. This helps assure that the operating room is not contaminated. Note that the space pressure (unlike temperature, humidity, or airflow) generally must be maintained at all times, even when the room is not in active use.

So how do you do all of this efficiently? We recommend a few different approaches. The first is to make sure you have the right requirements. Can humidity drift down to 20%? Can you keep the operating rooms closer to 70?F then 65?F? Do air changes need to be at 30 ACH or is 20 ACH OK? Finally, we have found the greatest savings through improved control of space pressurization. Using positive pressure controls that measure and control based on actual pressure differential between the OR and the adjacent sterile corridor is both more efficient and helps assure that you are maintaining and recording that pressure relationship. 

 Finally, consider adding in an unoccupied cycle. We find that most OR’s operate around 50 hrs/week, but are often fully conditioned 24x7. Adding an unoccupied cycle that allows temperature to drift reduces airflow, but it continues to maintain positive pressure when unoccupied and provides incredible energy savings. Generally in a medical center, one OR can be kept fully ready for emergency and the rest can readily come up to operating conditions within a few minutes if needed.   ES