As Australia ponders the challenge of reopening with COVID-19 still present in our communities, the discourse from government has focused on vaccination targets.
But increasingly, the public is demanding a more thorough response to the pandemic, incorporating other critical measures. Over the past weeks, one measure in particular has become front-page news: ventilation.
“Vaccination is vital,” says AIRAH CEO Tony Gleeson, M.AIRAH. “But for reopening to succeed, we must support it with other measures. Now that there is consensus that SARS-Cov-2 is airborne, why aren’t we doing more to address ventilation? This is particularly important in buildings such as schools, nursing homes, offices, shopping centres, cafés and restaurants.”
Gleeson says the situation is urgent, because although in some cases the solution is as simple as opening a window, other changes will take time.
“We know now that we should have invested earlier in dedicated quarantine facilities,” says Gleeson. “By the time that decision was made, we were already suffering the consequences. Let’s not make the same mistake again. The moment to act on ventilation is now.”
There seems to be widespread support from industry and the public for improving building ventilation. There is less clarity, however, about exactly what these improvements will be.
The old and the new
Brad Prezant, Affil.AIRAH, is Principal Consultant at Prezant Environmental and a member of AIRAH’s indoor air quality STG. He agrees that ventilation is key in minimising transmission. He suggests a two-pronged approach: one set of measures for new buildings, and another for existing buildings.
For new builds he says the first – perhaps controversial – step should be to stop using turbulent mixing ventilation systems.
“From an infection risk perspective, turbulent mixing is the least desirable air distribution strategy,” says Prezant. “It’s the worst possible design because you’re blowing the infective air all around the entire room and creating uniform mixing.”
Prezant notes that alternatives with laminar airflow, such as underfloor air displacement systems, chilled beams and personalised ventilation are all better at segregating infective exhaled material from other occupants. They have also been shown to be more energy efficient.
“We have technological solutions that satisfy both the infection risk minimisation for not just SARS-CoV-2 but all airborne infections, and the green building sustainability issues that are so important to everyone,” says Prezant.
“We ought to push for code requirements and other types of policy that will get new building systems designed for high indoor air quality.”
When it comes to existing buildings, Prezant has more than 30 years’ experience working with ventilation systems and addressing their failings.
Prezant says the first problems to address are often the result of poor maintenance or unnecessary operational constraints. A high-level assessment is a good first step.
“You go to a school and half the dampers are closed or disabled or dysfunctional or no one ever calibrated anything,” he says. “In a way we have to go back to basics – recommission, and identify any egregious problems. That’s so common in buildings, and the smaller the buildings get the more common it becomes because no one is looking at it.”
Prezant says many popular operational recommendations for HVAC systems in times of COVID do not always produce the best results.
“The way we’ve done it so far is to direct building operating engineers to open up the dampers and bring in more outside air and upgrade the filtration,” he says. “But those are actually not the lowest-hanging fruit, and can create unintended problems with humidity control, heating and cooling capacity, and operational cost.”
Another issue Prezant identifies is the often unpredictable airflows in buildings.
“HVAC engineers design the building and they’re very invested in believing that it’s operating the way they designed it,” he says.
“But when you’ve been diagnosing these buildings for decades and you see all these systems failing, you know they don’t behave the way they were intended to. If you glom together multiple fans, multiple systems, wind pressures, and the stack effect, they’re all influencing each other to create air movements both horizontally and vertically within a building across significant distances.”
Issues with hotel quarantine are a well-known example of this. Even after complex engineering reviews, transmission incidents were occurring between separate rooms because of unexpected airflows. Prezant has used tracer gas studies in various occupances to measure airflows. These have shown that airflow is not only occurring from rooms to hallways – the pathways that can be easily identified with a differential pressure measurement – but also along more complex pathways, for example from one floor to another floor, or from one room to another non-adjacent room.
“Differential pressure measurements do not tell the complete story,” he says. “Only tracer studies can identify these types of pathways.”
Prezant says that as well as recognising the complexity of building ventilation, engineers can start using tools to assess infection risk, such as COVID calculators. These work in a single space, such as a restaurant, and can also assist in a building with many separate spaces.
“It’s a very simple mathematical calculation to make,” says Prezant. “Using the example of a large building with a number of different rooms, if you know for each room what the flow in the terminal box is, you know the number of diffusers, you know the supply volume from those diffusers, you can easily calculate the air changes per hour, and combined with the size of the room and the activities within, create a rank order list of rooms by infection risk, and then begin remediating the highest risk spaces.
“That’s a much more fruitful approach, in my opinion – to take that overall perspective on the system and say how can we minimise the risk of infection. And the first solution may not be bringing more outside air and upgrading the filtration.”
At the moment, these risk infection models do not form part of the typical mechanical engineer’s toolkit.
“But they could easily learn to do that,” he says. “There are probably 25 free models out there that you could apply to a building.”
An investment for the future
Claire Bird, Affil.AIRAH, is President of the Indoor Air Quality Association of Australia (IAQAA) and is also a member of AIRAH’s IAQ STG. She says that ventilation will play a critical role in infection control, not only for COVID-19 but for future infection outbreaks.
“Ventilation can help in protecting us from new variants of COVID-19 while the vaccination program is evolving,” says Bird.
One area requiring special attention after reopening, says Bird, is transport.
“International travel between countries is likely to simultaneously reopen migration routes for new variants to enter Australia,” she says. “I believe that we need solutions for local, national, and international transport vessels, especially ships and aircraft where people share sufficient time to eat and drink, share public facilities, and may have to spend many hours in close contact with others. Unless phase four is managed to include airborne transmission controls, we may not be able to return to the future it promises in the long term.”
In terms of improving ventilation in buildings, Bird believes filtration offers significant opportunities.
“The industry could consider the correct use of air filtration and modification of systems to accommodate it where possible,” she says. “Certainly, working on ventilation improvements is critical as an industry.”
Professor Lidia Morawska has called on the World Health Organization to include airborne pathogens as part of any future indoor air quality guidelines. Bird says this will create a need in industry to design and manage buildings in a way that prevents airborne infection spread.
But she also says we must exercise caution when upgrading ventilation systems.
“Addition of commercial products in an HVAC system may not result in controlling the spread of an airborne infectious disease in a building,” she says.
“Care is needed by the industry in vetting the numerous products that claim to destroy viruses in air conditioning systems and so protect occupants. There remains little to no regulation around the use and installation of these products. A weak regulatory framework further adds to the concern around serious health risks from false advertising and needs urgent response from the industry.”
Bird says in the absence of leadership from government, the industry can help by providing clear and accurate information. Bodies such as IAQAA have been providing speakers on the topic of airborne transmission and respiratory diseases and free access to webinars. IAQAA is also among the organisations supporting the global multi-association Integrated Biosciences and Built Environment Consortium (IBEC) – a global body of leading scientists and practitioners across buildings, people and health assisting with the COVID-19 pandemic recovery.
“It will be providing a repository of condensed but accessible scientific information that is accurate and ‘uncontaminated’ by political or personal opinion,” says Bird. “Using such resources and keeping up with the latest and rapidly changing advice from government is important and proves a real challenge to the industry. And having a link to the government resources with daily updates on different regions and even postcodes in Australia is becoming critical when operating businesses.”
Bird emphasises that vaccination provides much hope, but cannot work in isolation.
“We should take reassurance from the fact that we no longer need to worry about polio, tetanus, smallpox, measles or whooping cough, providing we maintain a sufficiently high rate of vaccination,” she says.
“But the role of ventilation will not be any less important when we reach the fourth phase of opening. In fact, it may become even more important as we return to normalcy.
“We need our governments to take airborne transmission seriously and provide the infrastructure we need to design our buildings and other indoor spaces to mitigate health risks.”