BILLINGS, Mt.—Architecture, engineering, and design firm Cushing Terrell has developed what it calls a negative air pressure ventilation system designed to help prevent the spread of coronavirus infection between patients and healthcare workers. The firm recently worked with longtime client Billings Clinic to convert 100 patient rooms for the new paradigm, with a representative of the company saying Cushing Terrell “re-engineered, air balanced, and specified new supply and exhaust airflow for several bed floors in the hospital.”

In a recent interview posted on Cushing Terrell’s website, mechanical engineering group lead Shawn Murray said that it was critically important to create environments where covid-19 patients could be effectively treated while simultaneously keeping the possibility of infecting other patients and medical staff down to an absolute minimum. Accordingly, the firm’s negative pressure rooms are meant to contain, within a limited space, a patient’s exhalations since the main way that the coronavirus is spread from person to person is via airborne particles.

Murray said that the most effective way to treat covid patients would be to isolate them for treatment in “airborne infection isolation” (AII) rooms, but he added those rooms are extremely rare anywhere in the healthcare field. Accordingly, healthcare spaces that already exist would need to be “converted” to allow for negative air pressure situations.

“Air from these rooms does not recirculate into other areas of the hospital and is exhausted via dedicated ductwork where it is diluted in the atmosphere,” Murray was quoted as saying in the report. He added that patient rooms need to be quickly converted for negative air pressure given the ongoing nature of the pandemic, and should a future spike occur in Montana.

Although Cushing Terrell, which has many offices outside of their founding location in Billings, has performed work of this type on many other projects before, Murray’s contention is that this was the first time his company needed to simultaneously convert so many “standard” patient rooms for negative air pressure. In their writeup, Cushing Terrell quoted Murray as saying it was incumbent to “reconfigure enough rooms on the ICU floor where the intubation and extubation of ventilators for critical patients could create the highest risk for transmission to other areas of the hospital.”

This required overriding dampers on the air-handling units such that air which circulated throughout the patient rooms would instead be redirected directly to the outdoors. Murray said that this effectively changed the patient room “inlet air grilles into exhaust grilles” at locations throughout the Billings Clinic, including at nurse’s stations. Furthermore, certain inlet air grilles at the clinic were blocked such that additional exhaust air would be extracted from patient rooms, and thus “create a positive flow from the caregiver area into the patient rooms,” as Murray put it.

“Door sweeps” on patient doors were installed so that pressure differentials between patient rooms and the adjacent corridors could be equalized as well.

Murray added that one of the biggest challenges of the installation of the air pressure system was to foster a way to keep an operating room “positively pressured” along with the main surgery corridor, while rooms adjacent to the operating room had air in them that remained sterile. As such, one entrance had to be sealed and airflow redirected through what became the new anteroom outside the OR.

Murray said the project at the Billings Hospital also gave his firm a better idea of what future adjustments and improvements might need to be made to the HVAC system at the clinic.

Cushing Terrell has worked on air circulation and ventilation for various projects around the country. The firm was founded in Montana in 1938.

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A large medical office building in California presented the director of engineering at a Ruskin representative on the West Coast with an even bigger challenge – one he had never encountered in his almost three decades with the company. In addition to a system that used two large air handlers housed in two separate rooms on the building’s roof, a permanent pipe ran diagonally behind the building louvers in both rooms.

Pipe Presents Challenge

“Our task was to replace the components of the building’s large, built-up air-handling system,” the director of engineering explained. “This included the outside air louvers that cover a large opening in the building’s exterior and bring fresh air into the structure. What made this job somewhat out of the ordinary was the large structural steel pipe that ran behind the opening. The pipe could not be moved because it was part of the system designed to support the building in the event of an earthquake. Unfortunately, the pipe interfered with the installation of actuators on the jackshaft of the damper. Our job was to find a solution that compensated for the sheet metal wall separating the two rooms and provided a work-around for the pipe.”

In addition to replacing louvers and other key components of the air-handling system, operations managers at the medical office building planned to install dampers and air-measuring stations. The goal was to measure and control the amount of air entering the building, thereby meeting new building codes and standards that dictate how much fresh air a building must bring inside. An additional benefit would be an HVAC system with improved energy efficiency.

As he has in the past, the director of engineering turned to Ruskin for help. His company has served as a manufacturer’s representative for Ruskin for approximately 20 years. “During that time, we’ve always appreciated the quality of Ruskin products and the service of its people, who regularly apply their expertise to specific challenges.”

According to Rachel Larimore, sales application engineer at Ruskin, “We were challenged by the pipe and the thin, 18-gauge wall separating the two rooms. The project required a lot of back and forth to work out details, with four to five iterations of drawings to be certain we got everything right.”

Ruskin Provides Space-Saving Solution

For this project, Larimore recommended the Ruskin IAQ350XL. This unique, three-in-one product features a class A wind-driven rain louver, Class 1A-rated low-leakage damper and an integral air-measuring station in a common sleeve that is only 12 inches in the direction of airflow. Specifically designed to save space in tight mechanical rooms and air-handling units, the compact model reduces the space requirement by as much as 93 inches, when compared to typical air-measurement installation requirements, and provides accurate flow measurement to within ±3 percent accuracy.

“The IAQ350XL offers more variety and ways of doing things with air measuring,” added Larimore. “Prior to this project, the building featured plain louvers, with no dampers or air-measuring stations, which meant there was no ability to modulate or control air flow. The louvers just covered a large hole in the exterior of the building, providing protection from rain while letting in a constant flow of air.” If this were a residential property, Under House Ventilation would have been adequate, but this job called for an innovative approach.

Jackshaft Fits Around Pipe

Ruskin provided 14 sections of the IAQ350XL to cover the 336-inch by 118-inch opening. “They were able to fabricate the unit with a jackshaft that fit around the pipe. The units could also be adjusted in the field, which provided the installing contractor the flexibility to adjust as necessary to ensure a good fit. Additionally, those in charge of the building’s HVAC system can monitor all 14 sections and individually control them.”

The 14 IAQ350XLs are located on the roof, approximately 10 stories above the ground.

“The building owner was concerned they would need to rent a crane to get the units on the roof,” said Larimore. “Instead, we were able to fabricate the units in sections small enough to fit on a freight elevator, eliminating the costs associated with renting a crane.”

Today, the units allow the building to meet the standards and codes that dictate fresh air intake, while providing money-saving operating efficiencies.

“This project demonstrates the reasons our company continues to represent Ruskin products,” the director of engineering added. “Ruskin offers a variety of quality products that can be customized to meet the unique challenges we see in the field. In this case, they responded with a product that perfectly addresses space limitations by combining the functionality of three products in one. The result is a system that maintains proper ventilation and meets energy efficiency goals.”

Ruskin is an air control solutions company based out of Grandview.

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