The last few years have seen an increased focus on indoor air quality. Occupants want to feel comfortable in commercial spaces, and building owners, architects and engineers want to know that they’re constructing and renovating facilities with products that work as intended. No gimmicks – just real, science-backed solutions.
In 2021, inspired by the tremendous public interest about how we can better understand indoor air quality in commercial spaces, Price embarked on a research project that set out to do two things: quantify the efficacy of the different HVAC strategies intended to reduce airborne particulate counts and refine the methodology for testing indoor air quality.
| Research and Development Manager Ryan Johnson (left) and Sustainable Systems Product Manager Chris Burroughs (right) | |
Leading the project were Research and Development Manager Ryan Johnson and Sustainable Systems Product Manager Chris Burroughs, both of whom would go on to co-author a research paper detailing their findings. “For us in the air distribution world, when we’re designing ducts and moving air through a space, it’s immensely important to understand where particulates travel and whether we have a consistent way to improve the quality of the air,” said Ryan.
All tests were performed at Price Research Center North in Winnipeg, MB, in a “typical” office space (measuring 23 feet by 19 feet by 9 feet) that contained both a traditional overhead mixed-air system and a displacement ventilation system. The test room included four seated mannequins at a desk; one mannequin was equipped to emit particulates near its mouth, and sensor trees measured particulates at several locations throughout the room. A saline solution was used to generate inert aerosolized particles of varying size in the space. The team assessed the air distribution effectiveness of the two ventilation systems based on the measured particle concentration at different ventilation rates.
| The test setup at PRCN, complete with "office workers," sensor trees and saline atomizer |
The data confirmed that overhead mixed-air systems (like what you find in most commercial spaces) do evenly mix the airborne particulates throughout the space, including around the cubicle walls surrounding the mannequins. The displacement ventilation system resulted in a lower average particulate count at the occupant’s head height and below. The difference between the two systems was inconclusive in areas of the room away from the occupants, though this can be explained by displacement ventilation's reliance on a heat source to attract fresh supply air and there being no such heat sources in the corners of the room.
The team also found that a traditional tracer gas test did not provide the same exact results as a particulate count test. This was especially true for the displacement ventilation system, whose airborne particulate counts varied throughout the room in ways not clearly captured by a tracer gas. For context, tracer gases have historically been the primary means of quantifying air quality in these types of lab tests. The testing showed that tracer gas studies are not perfectly representative of the behavior of actual airborne particulates, which vary in size and mass – a finding that other researchers should consider in their own studies going forward.
| A computational fluid dynamics (CFD) contour plot comparing the particulate count for the mixed-air system (left) and the displacement ventilation system (right) |
Our hope is that these research findings can be one more “tool in the belt” of professionals who aim to improve the air quality in their spaces. Knowing that a displacement ventilation system has the potential to greatly reduce the number of airborne particulates near stationary, seated occupants, designers have another air distribution option to consider in building design – especially early on in their projects.
Translating findings into practical applications for the HVAC community is an art and a science. Being connected to organizations such as ASHRAE helps make new information widely available in a format that is accessible, easing the transition of taking the findings from the lab to the real world.
That’s why the team was so excited that the article was published in the December 2022 edition of ASHRAE Journal. You can read the full article, “Reducing Airborne Particulates Using Displacement Ventilation,” here.
| Watch this video to meet Ryan and Chris and to learn more about Price's research |
"We were really interested in getting our results out into the industry,” said Chris, “so that we as researchers can work together to make it digestible in a way that industry leaders, consultants and those actually designing our buildings can use that information.”
One of the team’s big takeaways from this project was that the controlled testing and measurement of airborne particulates is not a simple task; it requires top-notch instrumentation, experimental design and professionals to make it work. Price is excited to continue researching technologies related to indoor air quality, providing professionals with the science – and occupants with the peace of mind – that they’re looking for.