Insights from the Recent Indoor Air Quality Conference
At a recent industry-leading conference, international experts convened to address one of the most pressing questions in indoor air quality (IAQ): should CO₂ levels be regulated, and if so, how?
For years, carbon dioxide has been used as a convenient benchmark—often tied to ventilation performance. But as Professor Max Sherman pointed out, “CO₂ is not a contaminant at typical indoor levels—it’s a proxy. What we really want is clean air.”
The panel highlighted the importance of moving beyond simplistic metrics like 800 ppm of CO₂. Clean air, they argued, can be delivered through several means—including filtration and advanced air purification—not just by increasing outdoor air supply, which may be unsustainable in harsh climates.
Speakers also revisited the purpose of AS 1668, reminding attendees that it’s a design standard, not an IAQ performance or infection control benchmark. Voluntary standards like WELL and Green Star, on the other hand, are pushing the market forward—encouraging innovation, accountability, and better health outcomes across both new and existing buildings.
Notably, the discussion shifted toward particulate matter, especially PM2.5, as a more accurate reflection of respiratory risks. With airborne infection top of mind, this pivot signals a broader, science-based rethinking of how we define—and design for—healthy indoor environments.
Bottom line? CO₂ is part of the story, but it’s not the whole story. The future of IAQ lies in flexibility, evidence-based design, and a commitment to practical, sustainable solutions.
Evolution of HVAC in Disease Transmission: Key Points
There was discussions on the development of ASHRAE Standard 241, a landmark guideline created in direct response to the COVID-19 pandemic. It highlights how HVAC systems can play a crucial role in managing airborne disease transmission.
The pandemic revealed early misjudgments by health authorities about airborne transmission. In March 2020, ASHRAE formed an Epidemic Task Force to provide immediate guidance. Later, at the request of the White House, ASHRAE rapidly developed a formal standard—normally a 4–5 year process—within just four months, thanks to ‘tiger teams’ of experts.
Standard 241 introduced several key concepts:
1. Infection Risk Management Mode (IRMM): Designed to activate during outbreaks, not to run continuously. It applies to all building types and serves as a resilience tool for health protection.
2. Equivalent Clean Air (ECA): A pivotal concept that allows for multiple air-cleaning methods—such as ventilation, filtration, and purification—to be treated equally. ECA is scaled per person, not per air change, making it more adaptive and practical. Energy modeling shows compliance can be achieved with just a 10% increase in energy use when optimally implemented.
3. Air Cleaning Requirements: All air cleaners must be certified for both performance and safety. This includes filtration effectiveness and limits on harmful byproducts like ozone and formaldehyde.
4. Implementation Planning: Buildings must create readiness and maintenance plans. Additional care is required in residential settings, especially where infected individuals remain onsite.
The standard is currently under public review, with updates underway to better align it with existing ASHRAE standards and expand requirements around exhaust air.
This presentation showcased how the engineering community responded to public health demands by producing technically sound, flexible, and implementable infection control strategies for building environments.
Decarbonization in IAQ: Key Points from Ben Gill’s Presentation
Ben Gill’s presentation addressed how improved indoor air quality (IAQ) and decarbonization efforts can complement—not compete with—each other. He emphasized that with the right approach, buildings can achieve better health outcomes and lower emissions simultaneously.
His core message was clear: framing IAQ as being at odds with emissions reduction is a false dichotomy. Standards like ASHRAE 241 and Australia’s Standard 1668.2 offer frameworks that support both objectives.
Key insights included:
– Despite managing billions in commercial real estate over 17 years, Gill noted that indoor air quality was rarely a topic of discussion among building managers—highlighting a widespread gap in awareness and priority.
– ASHRAE 241 provides flexibility through three technology-agnostic strategies for infection risk reduction: dilution (via outdoor air), capture (through filtration), and destruction (using purification technologies).
A compelling case study from the University of Adelaide illustrated the benefits of proper intervention. An existing filtration system labeled as 85% effective was, in practice, only removing 48% of virus-like particles. After optimising the system, the particle count dropped from 1.8 million to approximately 30,000—while reducing air volume by 31.6% and cutting peak energy demand by 13 kilowatts.
Gill’s presentation underscored the opportunity for building owners and operators to adopt smarter, more sustainable IAQ strategies that also align with energy efficiency and emissions reduction goals.
