Key talking points from IAQ25

The theme of this year’s conference was “a pathway to change”, and there were certainly plenty of vibrant discussions about how to change IAQ for the better. And while participants didn’t always agree on approaches, the appetite for change was universal.

Here are some of the major discussions to emerge from the conference.

A 241 special

Dr Max Sherman from the Lawrence Berkeley National Laboratory was everywhere at the conference: as well as delivering the opening keynote presentation, he also participated in the Sunday workshop and the follow-up panel on Monday, as well as delivering a second presentation on day two.

Sherman’s keynote provided an in-depth introduction to ASHRAE Standard 241, a pathogen control standard for all building types that he played a key role in developing. As Sherman pointed out, 241 was developed in record time in response to COVID-19, but its utility extends far beyond just the current pandemic.

The standard introduces the revolutionary concept of an “infection risk management mode” (IRMM), which building managers can deploy at times of heightened risk. This functions like an on/off switch: for example, if there is an influenza outbreak in the city, building managers might activate IRMM until the outbreak subsides.

Another important aspect of 241 is the reference to “equivalent clean air” (ECAi) rather than air changes per hour. This means that, instead of mandating increased mechanical ventilation, 241 provides building managers with more flexible avenues to compliance. This could include enhanced air filtration, using UV technology to kill pathogens, or simply reducing the number or building occupants during that time.

The introduction of IRMM in 241 raised some philosophical questions that weren’t lost on the audience. As Dr Bronwyn King AO pointed out during the Q&A session, the COVID-19 pandemic remains ongoing, and people who are immunocompromised – and their families – are always at heightened risk from infectious diseases.

King posited that the IRMM specified in 241 should become a permanent requirement for buildings, though other participants pointed out this would likely increase energy costs and emissions. Finding the right balance – and technological solutions that could potentially address both issues – was an ongoing point of discussion throughout the conference.

Back to school

Several presenters – including Dr Richard J Shaughnessy, Mohamed Mahmoud, Stud.AIRAH, and Plum Stone – focused heavily on the importance of IAQ in schools, and the challenges faced in achieving not just acceptable, but accessible air quality.

Shaughnessy kicked off the second day of the conference with a fascinating dive into surface cleaning, its importance for IAQ, and its flow-on effects to occupant health, particularly in schools. He shared insights from his research team’s large-scale longitudinal study into cleaning in US schools, which spanned six years and included health data from 47,000 students across more than 50 schools.

Mohamed Mahmoud, Stud.AIRAH, from the University of New South Wales shared his research into classroom aerosol measurement using computational fluid dynamics simulations. His study compared a “stale air” classroom environment with two alternative setups: one HEPA filter and three HEPA filters.

Unsurprisingly, the setup with three HEPA filters was by far the quickest and most effective way to reduce the risk of infection. What was perhaps less expected was the effect of having a solitary HEPA filter in the classroom; this approach could actually spread the pathogen more quickly than having no filter. Despite this, Mahmoud clarified that HEPA filtration remains preferable to a stale air approach, and pointed out the importance of finding the right location for the filter(s).

Plum Stone from the Safer Air Project spoke about her organisation’s work in framing IAQ not just as a technical issue, but a critical accessibility and inclusion issue. Stone, who has immunocompromised family members and nearly lost one of her children to COVID-19, highlighted that this is not a niche issue. Roughly half of all Australians live with a chronic health condition that could put them at heightened risk from infectious diseases.

As well as focusing on healthcare facilities as sites of disease transmission, Stone also shared her concerns as a parent of two school-aged children. She posed a particularly poignant question about how inadequate classroom design and maintenance often puts the burden on children to control their ventilation by opening or closing windows:

Like Gill, Stone offered a pragmatic approach to policy change by highlighting that those making decisions are often more influenced by the economic and productivity benefits of improved IAQ than by the health and social benefits.

CO₂: contaminant or proxy?

One of the key talking points at IAQ25 began at the Sunday workshop, where experts debated whether we should consider CO₂ to be a proxy for air quality or a contaminant in its own right. You can read a wrap-up of the workshop on HVAC&R News.

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