Episode 100: 2 years of Conversations and the Future of Harm Metrics with Max Sherman
It is a significant milestone for the Air Quality Matters podcast. Two years, 1.5 million spoken words, and 100 episodes later, we return to where it all began. For this centenary episode, I sat down once again with my very first guest, the legendary Max Sherman .
For those in the built environment sector, Max needs little introduction. With a career spanning over 40 years at the Berkeley Lab , his fingerprints are on almost every major piece of air quality research and standardisation in recent history. But beyond the accolades, Max brings a candour and scientific rigour that cuts through industry noise.
We don't just look back at the post-pandemic landscape; we look forward to a fundamental shift in how we engineer indoor air—moving from arbitrary ventilation rates to quantifiable harm reduction.
The Convergence of Health and Engineering
One of the central themes Max and I explore is the maturing relationship between the medical community and building engineering. Historically, these disciplines have operated in silos: epidemiologists measure disease, while engineers measure flow rates.
Max argues that we are finally reaching a point where these two worlds can effectively communicate through data. We discuss the challenges of "longitudinal studies"—tracking exposure over 20 years—and how the industry is moving toward measuring success not by how much air we move, but by how much we reduce specific health risks. It is a nuanced discussion on how we are finally beginning to quantify the "cost" of poor air in a way that policymakers can understand.
The Harm Intensity Revolution
Perhaps the most compelling part of this conversation centers on the "Harm Intensity" work Max has championed. This represents a paradigm shift for standards like ASHRAE 62.2.
For decades, ventilation standards were often decided by "people in a closed room" negotiating consensus numbers for typical buildings. Max outlines a new, scientifically rigorous alternative: calculating the Disability-Adjusted Life Years (DALYs) associated with specific pollutants.
In the podcast, we dive into the "Big Three" contaminants that the data suggests are responsible for over 90% of the harm in residential spaces:
PM2.5: The overwhelming priority for engineering controls.
Formaldehyde: The "poster child" for source control and VOCs.
Nitrogen Dioxide (NO2): The proxy for combustion and outdoor pollution intrusion.
By focusing on these specific harms rather than a laundry list of 40+ chemicals, Max explains how engineers can optimize designs to save lives rather than just meeting a minimum code compliance checkbox. It is a fascinating look at how we can trade off different mitigation strategies to achieve a lower total harm score.
The CO2 Controversy
Listeners familiar with Max know he does not shy away from controversial opinions, and this episode delivers a standout moment regarding Carbon Dioxide.
While the industry has largely adopted CO2 monitoring as the de facto proxy for Indoor Air Quality (IAQ), Max offers a sharp, technical critique of this practice. We discuss why CO2 is an excellent tracer for ventilation rates per person but a potentially dangerous proxy for actual air quality or health—especially in the era of ASHRAE 241 and air cleaning technologies. Max effectively "throws a grenade" into the common perception that 800ppm automatically equals "healthy," arguing that we need to stop conflating ventilation effectiveness with contaminant control.
Why You Should Listen
This conversation is more than a retrospective; it is a forecast of where the industry is heading over the next decade. Max shares his personal 9-year goal to eliminate prescriptive ventilation rates entirely from standards in favor of harm-based performance metrics.
To understand the nuance of the "Harm Intensity" calculations, the distinction between "thresholds" and "optimization," and to hear Max’s thoughts on the future of IAQ standards, you need to hear the full exchange. It is a masterclass in the science that underpins the regulations we work with every day.
One Take: The State of Indoor Air in Australia 2025
Topic: Review of the "State of Indoor Air in Australia 2025" Report
In this edition of One Take, we turn our attention to a groundbreaking report coming out of the Thrive IAQ Research Centre: The State of Indoor Air in Australia 2025.
Australia has a long history of producing comprehensive "State of the Environment" reports, yet they have almost exclusively focused on the outdoors. This new report attempts to establish a national baseline for the indoor environments where Australians spend 90% of their time. The findings are sobering—not necessarily because of what was found, but because of what is missing.
The Baseline of Ignorance
The report included a systematic literature search of peer-reviewed papers since the year 2000. The researchers found that our collective understanding of Australian indoor air is based on a sample size representing less than 0.03% of the nation's building stock. Furthermore, 75% of these studies were concentrated in just two states (Queensland and Western Australia), leaving vast climatic and regional gaps in the data.
Key Insights
Despite the thin data, the report highlights critical "vignettes" of risk:
Bushfire Smoke: Standard housing provides limited protection during events, with HEPA filtration identified as a critical intervention.
Source Persistence: Formaldehyde from building materials was found to decay much slower than previously anticipated.
The TVOC Trap: The report reinforces that measuring Total Volatile Organic Compounds often masks specific risks from individual, high-toxicity compounds.
The Verdict
The true value of this report lies in its honesty. It authoritatively documents a national blind spot. It is not a manual of solutions, but a roadmap of the questions policymakers and building managers must now ask. It is a call to move from isolated snapshots to a coordinated national strategy for the great indoors.
State of Indoor Air in Australia Report 2025
The Air Quality Matters Podcast in Partnership with
Zehnder Group - Farmwood - Eurovent- Aico - Aereco - Ultra Protect -
The One Take Podcast in Partnership with
SafeTraces and Inbiot
Do check them out in the links and on the Air Quality Matters Website.
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