Designing positive and negative isolation rooms

To minimize the spread of airborne infections, certain rooms within a hospital are designed with either negative or positive pressure.

By RTM Engineering Consultants, Ill. January 19, 2017

In health care facilities, airborne infectious disease is a serious concern that poses a threat to patients, staff, and visitors. To minimize the spread of airborne infections, certain rooms within a hospital are designed with either negative or positive pressure.

RTM has extensive experience planning negative- and positive-pressure isolation rooms within health care facilities. The company’s expert engineers collaborate closely with architects early in the design process and also work with hospital staff to ensure that the rooms are mechanically optimized after they’ve been constructed.

"The earlier we get involved, the easier it is to identify possible issues ahead of time," said RTM Associate Marty Herrick, PE. "We provide high-level engineering support throughout the project, assessing how our mechanical expertise will better serve these rooms, protect the patient, and optimize efficiency. We work with the architect to find the best solution from a programming standpoint to determine where supply air will come in and where exhaust will go out to meet the hospital staff’s needs."

Negative-pressure isolation rooms

A negative-pressure room is designed to isolate a patient that is suspected of, or has been diagnosed with, an airborne infectious disease. The negative-pressure isolation room is designed to help prevent the spread of the disease from the patient to others in the hospital.

Negative-pressure rooms require a minimum of 12 air changes of exhaust per hour and are required to maintain a minimum 0.01-in.-water column (wc) negative-pressure differential. Depending on factors such as room size, orientation, and the number of windows present, more than 12 air changes per hour may be necessary. A negative-pressure isolation room typically is served by a dedicated exhaust fan. Some health care facilities also use UV radiation to disinfect rooms after a patient has vacated the room.

Positive-pressure isolation rooms

A positive-pressure isolation room is designed to keep contagious diseases away from patients with compromised immune systems, such as cancer or transplant patients.

Positive-pressure rooms also require 12 minimum airflow changes per hour and are required to maintain a minimum 0.01-in.-wc positive-pressure differential, ensuring that the patient is protected from airborne contamination; more than 12 changes may be necessary depending on the room size and orientation. Positive-pressure rooms also typically use high-efficiency particulate air (HEPA) filters at the supply terminals to ensure the cleanest air possible for the patient. Positive-pressure isolation rooms appear similar to standard patient rooms, but they use a higher airflow.

When planning both types of isolation rooms, RTM engineers work with architects to design effective spaces that will maintain the pressure differential. Wall and penetration joints must be tightly sealed. Factors that can affect pressure, such as anterooms or sliding doors, also have to be taken into account.

"We’ve performed the design for isolation rooms many times. We can help the project team better understand how the systems need to operate," said Herrick.

When designing isolation rooms, RTM brings expert engineering knowledge that maximizes patient safety while also helping the facility to minimize energy consumption and operating costs. "We help clients in identifying, prioritizing, and implementing energy improvements, of which they qualify for, to key building systems as we go through the design process," Herrick noted. "When not required for isolating an infectious patient, you may be able to run an isolation room as a standard patient room. By turning a key switch on the wall, the room operates at a lower-exhaust airflow, saving the owner energy." 

-This article originally appeared on the RTM Engineering Consultants blog. RTM Engineering Consultants is a CFE Media content partner.