This Firm Rejiggered a Health Care Clinic’s HVAC System to Create Negative Air Pressure in 100 Rooms

Paul Doherty’s proposal to reduce COVID-19’s spread in buildings through negative air pressure is getting a real-life test at a clinic in Billings, MT. That city’s Billings Clinic dramatically increased its number of airborne infection isolation (AII) rooms by adjusting the facility’s HVAC system to dramatically increase the number of potential rooms for coronavirus patients.

Airborne infection isolation rooms differ in that the negative air pressure inside them causes air to flow into the room; the air then is exhausted through dedicated ducts to outside the hospital. Such rooms, designed to ASHRAE 170 guidelines, protect patients elsewhere by keeping them from breathing air that might have been in the room previously. This is particularly important if the isolation room has a COVID-19 patient, given how the virus commonly infects others by traveling through the air from one person to another.

Cushing Terrell, an architecture/engineering/design firm based in Montana, worked at night and on weekends to convert 100 patient rooms into negative pressure isolation rooms. “With what we’ve learned and experienced so far as a result of the pandemic, a reliance on untreated recycled air will likely become a thing of the past,” said Shawn Murray, who leads Cushing Terrell’s mechanical engineering group. “…These technologies and systems that reduce viruses, bacteria, allergens, odors, and other particles will become increasingly important, not only in healthcare facilities, but in all public buildings and facilities.”

Cushing Terrell also created the ability for surgery rooms to go from positive to negative air pressure at the flick of a switch.

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