Mark Vender
On May 15, the eyes of the global HVAC&R community were trained on the US, as ASHRAE released the first draft of Standard 241P Control of Infectious Aerosols. The standard provides minimum requirements for HVAC-related measures to reduce the risk of transmission of COVID-19, influenza, and other airborne viruses in homes, offices, schools, and hospitals during periods of high risk.
It has been a remarkably fast turnaround for such a major piece of work, which began in December last year at the behest of the White House. And the timelines for finalising and publishing the standard are equally as ambitious. Comments close May 26, with final approval expected in June, and publishing anticipated in July.
Given that this project has involved experts from around the world, and has been spurred by a clearly stated government goal of improving indoor air quality, Australia may well ask whether the work can help us make a much-needed leap forward.
HVAC&R reached out to three Australian IAQ experts for their views on the standard – and its implications for Australia.
Standard adaptable for local use
Melbourne-based Brad Prezant, Affil.AIRAH, is Principal Consultant at Prezant Environmental and a member of AIRAH’s Indoor Air Quality Special Technical Group. He has a clearer view of the ASHRAE standard than most, having worked as part of the project committee.
“Overall, the content is comprehensive and the speed at which it all came together is remarkable,” he says. “There were many people with significant expertise devoting many hours to the draft, and as a participant it was a unique exercise. The chairs and sub-group chairs took on an extraordinary task and completed it well.”
According to Prezant, the initial public comments on the draft have been “significant and copious” – which will be reflected in the final version. When it is published, Prezant says he would very much like to see Standards Australia review and adapt the ASHRAE standard for use in Australia.
“There is sufficient similarity in building HVAC system design and operation between the US and Australia that there would be considerable applicability in many of our most populated cities,” he says.
As well as the ASHRAE standard, the CDC has recently updated its advice on ventilation in buildings. Prezant notes that these recommendations are based on air changes per hour (ACH), while the approach in Standard 241P is to consider risk of infection and level that move across different space types with occupancies (assumed according to ASHRAE Standard 62.1) independent of ACH.
“The two approaches are different,” he says, “with advantages and disadvantages of each, and varying implications based on different space characterisations of volume and ACH. Note that ASHRAE 62.1 makes certain assumptions regarding occupancy and space volume, all of which influence risk of infection through their impact on ACH and ultimately concentration of ‘quanta’ – infected particulate – in the air in the far field. It is this metric that most impacts risk of infection, along with time of occupancy and activity rate, which define the dose of what is airborne.
“These complexities are still being worked out in the context of dovetailing with other recommendations, such as the CDC guidance on ACH.”
The recent initiatives around ventilation suggest that the US is taking a more proactive approach to IAQ. But Prezant says there is some way to go.
“Generally, there has been more talk than action both in Australia and in the US,” he says. “Whether this talk leads to meaningful change will depend on market forces and/or government mandates through the standards process and building codes.
“In the case of voluntary compliance programs that include indoor air quality criteria, such as NABERS, Green Star, and WELL, the market in Australia has created significant momentum and adoption, at least in office spaces among developers and owner-occupiers. So, market forces can be quite effective – and have been here in Australia.
“If we were to simultaneously develop more government-based mandatory standards for indoor air quality that include but extend beyond infection management to more general indoor air quality considerations, we would be taking these issues much more seriously, with actions that can really make a difference for health and productivity.
“Scientists have spoken out on the importance of these issues; it is up to the professional organisations and the politicians to sustain the momentum.”
A significant contribution to the Australian market
Dr Claire Bird, Affil.AIRAH, is Secretary of the international Integrated Biosciences and Built Environment Consortium (IBEC), and Co-chair of the AIRAH IAQ STG, and in this position has been coordinating members’ responses to the draft standard.
She notes that the draft standard primarily focuses on tackling the long-range transmission of infectious aerosols rather than between people at close quarters, outlining the minimum requirements for buildings to adopt when they enter infection risk mitigation mode (IRMM).
“In simpler terms, this mode aims to minimise the risk of infection when it is at its highest,” says Dr Bird. “The current document concentrates on establishing thresholds for equivalent outdoor air exchange rates. These thresholds are based on the combined impact of ventilation, filtration, and air cleaning, whenever necessary, to achieve the desired values during periods of high risk of transmissible airborne disease.
“Additionally, the standard provides recommendations for minimum HVAC maintenance tasks and their frequency. It also offers guidance for reducing infection risk in residential and healthcare settings. Therefore, I can confidently say that the standard will make a significant contribution to the Australian market.”
Dr Bird highlights that the standard also delves into the realm of reducing infection transmission risk by optimising room air distribution, evaluating the effectiveness and safety of filters and air cleaners (with regard to unintended emissions), and emphasising the importance of commissioning.
She also notes the standard’s requirements around air supply requirements.
“Some settings require at least doubling the current outdoor air supply. For instance, offices operating in IRMM mode will be required to achieve a rate of 20L/s/person of pathogen-free air, while gyms will need to reach 40L/s/person.”
Dr Bird says that at first glance, there seems to be less emphasis on preventive measures aimed at improving general air quality and reducing lower levels of infection spread.
“However, it is worth mentioning that the testing components of the standard are applicable to filters and technologies deployed for day-to-day enhancements in air quality,” she says.
Although Dr Bird agrees that efforts to improve indoor air quality in Australia have been slower, potentially influenced by the rapid uptake of vaccinations in the country, she says that good work is being done.
“Groups of dedicated scientists, such as those associated with IBEC globally and the scientists involved with OzSage in Australia, have consistently emphasised the significance of airborne transmission as the primary route of infection for respiratory diseases, right from the early stages of the COVID-19 pandemic.
And she stresses that COVID-19 is not the only concern.
“We continue to encounter challenges regarding the transmission of airborne pathogens,” she says. “The rise in cases of respiratory syncytial virus (RSV), influenza, and infectious Group A Streptococcal disease (including childhood pneumonia) leading to hospitalisations and severe illness underscores the importance of implementing measures to mitigate pathogen transmission. Furthermore, the persistent growth in the number of patients experiencing long-COVID complicates the assessment of when we can safely transition from an infection risk mitigation mode (IRMM). It is clear that we are still in a phase where pathogen transmission mitigation remains crucial.”
Reasons to be optimistic
Dr Jason Monty is Professor of Fluid Mechanics and head of the Department of Mechanical Engineering at the University of Melbourne. He says parts of the ASHRAE standard could definitely be adapted for Australia.
Like Dr Bird, he notes the high equivalent outdoor air rates for infection control.
“The airflow rates in this document are very, very high,” he says. “In some cases, recommended airflow rates per person are as high as 90L/s/person, which is six times higher than even the WHO recommendation for ventilation.
“Of course, this is only for pandemic preparedness, not for regular ventilation settings. This has particular importance for hospitals. Future design guidelines and construction codes for hospitals, aged care and other sensitive settings should take note of this new standard.”
Dr Monty points out that the standard provides a comprehensive set of guidelines and methods to calculate equivalent outdoor air (EOA) within a space.
“Importantly, this is not only ‘outdoor’ or ‘fresh’ air, but rather the combination of outdoor and fresh air with ‘cleaned’ air,” he says. “The cleaned air may come via portable HEPA filters or UVGI.
“It is excellent that ASHRAE are taking this comprehensive view, which gives facilities managers, building engineers, designers and tenants the opportunity to design for safe air via combined methods for delivering ‘clean’ air. Previously these have been separated, and one is left to consider either HVAC upgrades/changes or alternative air-cleaning methods. Now both can be considered together – or one could design for ‘pandemic mode’, where HVAC does regular-time work and during an infectious disease outbreak, extra cleaning technologies could be brought online according to this standard.”
The US action on IAQ reflects how quickly the issue was prioritised by government, says Dr Monty.
“Some ministers in the federal government invited the majority of clean air experts in Australia to the Clean Air Forum in Canberra on March 25, 2023,” he says. “Joe Biden’s administration hosted their Clean Air Summit in June, 2022. Optimistically, we are one year behind the USA on this issue.
“There is reason to be optimistic that Australia will take indoor air quality more seriously in the short-term. New standards in other countries, such as these ASHRAE standards, will only help us in our campaign, since Australia often adopts such standards and is likely to respond with our own changes to codes, standards and guidelines as a result.”
Photo by Önder Örtel on Unsplash
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