Air Quality Matters

This week, we dive into a fascinating paper from Douglas Booker published in the journal Athermira titled Unstable Air: How COVID-19 Remade Knowing Air Quality in School Classrooms, to explore a question that fundamentally challenges how we think about indoor air quality intervention: What if the single most important lesson from the pandemic isn't that we need to measure air quality—but that we need to fundamentally rethink who is responsible for fixing it, and whether our solutions are creating entirely new problems?

This paper offers a rare behind the scenes look at an applied indoor air quality research project that got completely hijacked and subsequently reshaped by the global pandemic. It examines how our understanding of what makes air good or bad is not just a scientific fact but something that shifts based on society, politics, and in this case, a novel virus.

Key Topics Discussed:

The Original Mission: Before COVID, researchers deployed sophisticated air quality monitors into 20 school classrooms across England and Wales to measure traditional pollutants—ultrafine particles, nitrogen dioxide, VOCs—things infiltrating from outside or off-gassing from furniture. The goal was straightforward: measure the bad stuff and see how effectively air cleaners could scrub it away.

The Pandemic Pivot: When COVID hit, the entire narrative flipped. Suddenly the greatest source of indoor air pollution wasn't traffic or cleaning products—it was human breathing. We became the source of contamination. The project had to adapt, but hit a microscopic hurdle: how do you actually measure a virus in the air when your monitors just count particles without telling you what they are?

The Carbon Dioxide Proxy: Unable to isolate viral particles, researchers pivoted to a reliable proxy: carbon dioxide. By watching CO2 levels rise and fall, they could measure how much air in the room had already been in someone else's lungs and calculate ventilation rates. Pre-COVID data showed classrooms regularly exceeded recommended limits. But graphs alone don't change behaviour.

The Wells Riley Translation: To translate numbers into risk, researchers used the Wells Riley equation to calculate airborne infection probability. The results were powerful: in one scenario, low ventilation created an 80% probability of infection. Simply increasing airflow to 100 cubic metres per hour dropped that to 40%. Small ventilation improvements created massive risk reductions.

The Milk Out of Your Tea Problem: In the rush to dilute the virus by opening windows, we might be trading one severe health risk for another. If your school sits on a busy urban road, opening windows drops CO2 and virus risk but floods classrooms with toxic traffic fumes. Running a portable air cleaner with windows wide open to a polluted street is like trying to take milk out of your tea.

The Inequality of Personal Responsibility: By handing out CO2 monitors and telling teachers to manage windows, the government effectively individualised air quality. The message: here's a blinking light, fixing it is your responsibility.

Unstable air: How COVID-19 remade knowing air quality in school classrooms https://www.researchgate.net/publication/378714580_Unstable_air_How_COVID-19_remade_knowing_air_quality_in_school_classrooms

The Air Quality Matters Podcast in Partnership with

Particles Plus https://particlesplus.com/

Eurovent (https://www.eurovent.eu/) - Aico (https://www.aico.co.uk/) - Lindab (https://www.lindab.ie/)

The One Take Podcast in Partnership with

SafeTraces (https://www.safetraces.com/) and Inbiot (https://www.inbiot.es/?utm_campaign=simon&utm_source=airqualitymatters&utm_medium=podcast) - Farmwood (https://farmwood.co.uk/)

Do check them out in the links and on the Air Quality Matters Website. (https://www.airqualitymatters.net/podcast)

If you haven't checked out the YouTube channel its here (https://www.youtube.com/@airqualitymatters-SimonJones). Do subscribe if you can, lots more content is coming soon.

Chapters

00:00:00 Introduction: The One Take Format and Unstable Air
00:01:27 The Outdoor Air Quality Paradox: Why We Ignored Indoor Spaces
00:02:30 The Original Mission: Measuring Classroom Pollutants in 2020
00:03:18 The Pandemic Pivot: When Humans Became the Pollution Source
00:03:58 The Measurement Problem: You Can't See a Virus in Particle Counts
00:04:33 The CO2 Proxy Solution: 150 Years of Measuring Bad Air
00:05:57 The Wells-Riley Equation: Translating Numbers Into Infection Risk
00:07:18 From Concern to Care: The Ethical Intervention That Worked
00:08:25 The Window Paradox: Trading Viral Risk for Toxic Fumes
00:09:35 The Inequality Problem: When Air Quality Becomes Personal Responsibility
00:10:23 The Critical Future: Building Better Pandemic Infrastructure

This week, we sit down with Christopher Mueller, Global Director of the High Purity Segment at AAF International (American Air Filters), to explore a question that fundamentally challenges how we think about indoor air quality: What if the single biggest gap in our approach to healthy buildings isn't particulate filtration—but our complete failure to address the invisible chemical soup we're breathing every single day?

Chris brings over 40 years of deep expertise in environmental air quality and gas phase air filtration. With more than 200 peer reviewed papers, hundreds of seminars, and co authorship of major industry handbooks including the NAFSA Air Filtration Handbook and ASHRAE standards, Chris has testified at OSHA on indoor air quality standards and consulted with governments worldwide. He is the former chair of ASHRAE 145, which developed the first standard for assessing gas phase air filtration media performance, and remains a member of key technical committees shaping the future of air cleaning globally.

Key Topics Discussed:

The Fundamental Difference: Particulate filtration is catching. Gas phase filtration is reacting. Gases move by diffusion, from high to low concentration, and removing them requires adsorption—getting molecules out of the air and onto the surface of materials like activated carbon, alumina, or zeolites. Unlike particle filters, gas phase filters don't fill up. They run out. They lose effectiveness over time, and there's no pressure gauge to tell you when.

Surface Area Is Everything: Most activated carbons have around 1100 square meters per gram of surface area. That's not the exterior of the pellet. That's the interior pore structure. Volatile organic compounds get inside, condense back into liquid form, and stay there. The physics of adsorption depend on molecular weight, concentration, residence time, and contact efficiency. You need the air to touch the adsorbent before it exits the filter.

One Filter Won't Do It All: You can't use one type of gas phase media to remove everything. Basic activated carbon handles many organic compounds. Acid gases like sulfur dioxide require chemically treated carbon. Ammonia requires another type entirely. Think of it like particulate filtration: pre filter, intermediate filter, final filter. Same logic applies to chemicals.

The Four Global Markets: Corrosion control accounts for 60 to 65 percent of the global gas phase filtration market, driven by electronics manufacturing, data centers, and industrial facilities where chemical contamination voids equipment warranties. Wastewater odor control is second. Indoor air quality in commercial buildings is third. Airborne molecular contamination in semiconductor manufacturing is fourth. The total global market is approximately $2 billion and growing at 5.5 percent annually.

GUEST:

Christopher Mueller

Global Director, High Purity Segment, AAF International

https://www.linkedin.com/in/chrismullerconsulting/

AAF International https://www.aafintl.com/

The Air Quality Matters Podcast in Partnership with

Particles Plus https://particlesplus.com/

Eurovent (https://www.eurovent.eu/) - Aico (https://www.aico.co.uk/) - Lindab (https://www.lindab.ie/)

The One Take Podcast in Partnership with

SafeTraces (https://www.safetraces.com/) and Inbiot (https://www.inbiot.es/?utm_campaign=simon&utm_source=airqualitymatters&utm_medium=podcast) - Farmwood (https://farmwood.co.uk/)

Do check them out in the links and on the Air Quality Matters Website. (https://www.airqualitymatters.net/podcast)

If you haven't checked out the YouTube channel its here (https://www.youtube.com/@airqualitymatters-SimonJones). Do subscribe if you can, lots more content is coming soon.

Chapters

00:00:00 Introduction: Meeting the Gas Phase Air Cleaning Guru
00:02:51 The Fundamental Difference: Particulate vs Gas Phase Filtration
00:09:29 The Science of Adsorption: How Gas Phase Filters Actually Work
00:17:10 The Swiss Cheese Approach: Multi-Stage Gas Phase Filtration
00:23:20 Form Factors and Physical Products: From Pleats to Packed Beds
00:28:00 Precision and Specificity: Can You Target Individual Chemicals?
00:34:20 The Four Markets: Where Gas Phase Filtration Is Applied Today
00:38:24 Corrosion Control: The Hidden Giant of Gas Phase Filtration
00:44:00 Indoor Air Quality and the IAQP Opportunity
00:48:38 The Commercial Reality: Why Gas Phase Is Still a Hard Sell
01:13:49 Materials and Sustainability: What Is Activated Carbon Made From?
01:24:13 The Path Forward: Education, Standards, and Market Evolution
01:36:35 Closing Thoughts: Making the Invisible Visible

This week, we dive into a groundbreaking computational fluid dynamics study from KTH Royal Institute of Technology in Sweden that fundamentally challenges how we think about portable air cleaners in care homes: What if the single most important decision about air cleaning isn't which device you buy—but where you put it in the room?

During the height of the COVID-19 pandemic, care homes experienced devastating mortality rates among elderly residents. These environments are uniquely challenging—combining elements of healthcare facilities with residential living spaces, housing vulnerable populations who spend prolonged periods indoors with limited mobility and compromised immune systems. Portable air cleaners emerged as a promising, accessible solution. But does it actually matter where you place them? Can you just plug them in wherever the cable reaches and assume the job is done? And critically, will the airflow create cold drafts that make elderly residents so uncomfortable they simply switch the device off?

Key Topics Discussed:

The Care Home Challenge: Why care homes represent such a unique built environment challenge. Vulnerable populations with reduced mobility, chronic illnesses, compromised thermoregulation making them sensitive to drafts, and prolonged indoor exposure without control over their immediate environment. Any intervention has to work within these constraints.

The 74% Variation Problem: Using computational fluid dynamics simulations, researchers tested the same portable air cleaner in nine different locations within a typical care home room. The result: placement alone created a 74% variation in infection risk. Same machine, same room, same people—completely different outcomes based purely on where the device sat.

The Worst Case Scenario: In one placement configuration, positioning the air cleaner near the infected healthcare worker created a powerful airflow jet that actively transported exhaled virus particles directly into the breathing zone of the elderly patient. The infection risk skyrocketed to 85.9%. The air cleaner didn't just fail—it made things dramatically worse.

The Best Case Scenario: Placing the air cleaner in the centre of the room created the lowest infection risk—75 to 86% reduction compared to no air cleaner—by forming an invisible air barrier between occupants. But it's completely impractical due to tripping hazards in environments with wheelchairs, walking frames, and elderly residents with limited mobility.

The Thermal Comfort Win: Across all tested scenarios, draft rates remained below the 10% discomfort threshold. This is critical. There's no point achieving perfect air quality if the occupant is freezing cold and turns the device off. The study proves portable air cleaners can reduce infection risk without compromising thermal comfort—if used correctly.

The Training Gap: The on demand, plug and play nature of portable air cleaners means frontline workers—nurses, cleaners, facility managers—play a critical role in their effectiveness. Without proper training and clear visual guidance showing safe placement zones, we risk unintended consequences. Procurement isn't enough. Education is essential.

CFD study on performance of portable air cleaner on infection risk and draught rate in care homes https://doi.org/10.1016/j.indenv.2026.100151

The Air Quality Matters Podcast in Partnership with

Particles Plus https://particlesplus.com/

Eurovent (https://www.eurovent.eu/) - Aico (https://www.aico.co.uk/) - Lindab (https://www.lindab.ie/)

The One Take Podcast in Partnership with

SafeTraces (https://www.safetraces.com/) and Inbiot (https://www.inbiot.es/?utm_campaign=simon&utm_source=airqualitymatters&utm_medium=podcast) - Farmwood (https://farmwood.co.uk/)

Do check them out in the links and on the Air Quality Matters Website. (https://www.airqualitymatters.net/podcast)

If you haven't checked out the YouTube channel its here (https://www.youtube.com/@airqualitymatters-SimonJones). Do subscribe if you can, lots more content is coming soon.

Chapters

00:00:00 Introduction: The One Take Format and This Week's CFD Study
00:01:03 The Care Home Crisis: Why COVID-19 Hit the Elderly So Hard
00:01:37 The Vulnerable Population: Mobility, Immunity, and Thermal Sensitivity
00:02:09 The Portable Air Cleaner Promise: Easy Solution or Placement Problem?
00:02:50 The CFD Simulation: Mapping Invisible Airflow and Virus Particles
00:03:43 The Good News: 75-86% Risk Reduction Without Creating Drafts
00:04:26 The Shocking Discovery: 74% Variation Based on Placement Alone
00:04:58 The Worst Case Scenario: When Air Cleaners Blow Virus Directly at Patients
00:05:45 The Best Placement Dilemma: Center of Room vs Practical Safety
00:06:47 The Real World Lesson: Education, Training, and Strategic Deployment

This week, we sit down with Mikael Börjesson, Future Solutions and Public Affairs Director at Swegon Group, to explore a question that fundamentally challenges how we think about sustainability in the HVAC industry: What if the biggest transformation in ventilation isn't about technology or performance anymore—but about fundamentally rethinking how we manufacture, install, use, and reuse the systems that keep our buildings breathing?

Mikael works at the intersection of innovation, sustainability, and public policy, with deep roots in the sector and vast experience in stakeholder engagement, industry collaboration, and EU regulatory frameworks. He brings a rare perspective—someone who sees both the internal pressures on manufacturers to decarbonize their supply chains and the external pressures from investors, policymakers, and end users demanding transparency, circularity, and accountability.

Key Topics Discussed:

The Two Wallets Problem: How sustainability has moved from a marketing exercise to a genuine accounting challenge. There's the traditional wallet—cost, performance, energy efficiency. And now there's the sustainability wallet—embodied carbon, circularity, material choices. Both need to be satisfied, and they don't always align.

Embodied Carbon is the New Battleground: In renovations, HVAC installations can represent 40 to 60 percent of the total carbon footprint of a project. Suddenly, ventilation manufacturers are no longer a marginal cost—they're a major driver of sustainability outcomes. That changes the conversation entirely.

Circularity is Here—And It's Real: Swegon has already completed its first fully circular project—air handling units, diffusers, and dampers refurbished, remanufactured, and reinstalled alongside new low-carbon components. No extra cost. No performance compromise. Just a fundamentally different way of doing business.

The Stakeholder Chain is Broken: The traditional construction supply chain—investor, designer, installer, service technician—is built for linear consumption. Circularity requires a completely different model, with new roles, new relationships, and new risks. Some stakeholders will become obsolete. Others will emerge. The transition is messy.

The Harmonization Problem: Environmental Product Declarations are becoming the standard way to communicate embodied carbon. But they're calculated differently across different standards, different product categories, different regions. The result: you can't compare products. The industry needs harmonization urgently

GUEST:

Mikael Börjesson

Future Solutions and Public Affairs Director, Swegon Group

https://www.linkedin.com/in/mikael-b%C3%B6rjesson/

https://www.swegon.com/

https://www.swegonairacademy.com/

The Air Quality Matters Podcast in Partnership with

Particles Plus https://particlesplus.com/

Lindab (https://www.lindab.ie/) - Eurovent (https://www.eurovent.eu/) - Aico (https://www.aico.co.uk/)

The One Take Podcast in Partnership with

SafeTraces (https://www.safetraces.com/) and Inbiot (https://www.inbiot.es/?utm_campaign=simon&utm_source=airqualitymatters&utm_medium=podcast)

Do check them out in the links and on the Air Quality Matters Website. (https://www.airqualitymatters.net/podcast)

If you haven't checked out the YouTube channel its here (https://www.youtube.com/@airqualitymatters-SimonJones). Do subscribe if you can, lots more content is coming soon.

Chapters

00:00:00 Introduction: Meeting Mikael Bowieson from Swegon Group
00:02:23 The Sustainability Evolution: From Energy Efficiency to Embodied Carbon
00:11:52 The Two Wallet Problem: Balancing Cost and Carbon
00:14:20 Having Difficult Conversations: When Sustainability Meets the Supply Chain
00:19:39 The Consumption Paradox: Growth vs Sustainability
00:26:28 Scope Emissions and the Middle of the Supply Chain
00:30:02 The Circular Economy Journey: Reuse, Remanufacture, and New Business Models
00:39:12 The Real Project: Circular HVAC in a Swedish School
00:41:00 Breaking the Chain: What It Takes to Scale Circular Business Models
00:44:00 The Carrot and the Stick: Policy, Incentives, and Market Drivers
00:46:12 Renovation Reality: Where HVAC Becomes 40 to 60 Percent of Carbon Impact
00:33:12 The Harmonization Problem: Making EPDs Comparable
01:13:32 Future Solutions and Public Affairs: A Dual Role Explained
01:17:21 Innovation Hunting: Finding the Next Generation of HVAC Solutions
01:27:47 The Interoperability Challenge: Making Complex Building Systems Work Together
01:31:18 Learning from Cars: Why Buildings Need Self-Diagnosing Systems
01:02:37 The Indoor Air Quality Awareness Gap: Why We Track Outdoor but Ignore Indoor
01:09:46 The Public Health Case: Indoor Air Quality Equals Smoking in Health Impact
01:11:48 The Investment Problem: Who Benefits vs Who Pays
01:41:53 The Weakest Link Paradox: When the Strongest Part of the Chain Holds Back Progress

This week, we sit down with Ben Jones, Associate Professor at the University of Nottingham and one of the lead authors of AM10, CIBSE's guide to natural ventilation in non-domestic buildings, to explore a question that fundamentally challenges how we think about ventilation strategy: What if the oldest approach to ventilation—natural airflow—still has a critical role to play in some of the most advanced buildings we're designing today, and what if we've been making the same mistakes for decades because we never really understood the fundamentals?

After a decade in development, AM10 has been completely rewritten for 2026—not just to update the maths, but to make natural ventilation accessible, understandable, and practical for everyone from salespeople to architects to engineers who need to know whether natural ventilation is even feasible for their project before they waste time and money chasing the wrong solution.

Key Topics Discussed:

Why AM10 Needed Rewriting: The 2005 version was intimidating, dense, and assumed too much prior knowledge. The 2026 version is structured in layers—chapter two is designed so that anyone, from a student to a salesperson, can understand the basic physics. If you want the deep maths, it's there. If you just need to know whether natural ventilation will work for your building, you can get that answer quickly.

The Physics Made Simple: Warm air rises. Pressure differences drive flow. Wind complicates everything. But somewhere on every facade, there's a neutral pressure level where the sign flips—where air stops coming in and starts going out. Controlling that point is the essence of natural ventilation design. Get it wrong, and your building doesn't breathe.

Effective Area vs Free Area: One of the biggest changes in AM10 is how openings are measured. Combining free area with discharge coefficients into a single effective area metric forces window manufacturers to actually test their products aerodynamically and gives engineers a real number they can design with. No more fudging the geometry.

Single-Sided Ventilation Gets Smarter: The old equations were too simplistic. The new version accounts for recirculation zones in large openings—where air comes in at the bottom, goes out at the top, and mixes in the middle. It accounts for wind-driven turbulent mixing. The result: better-sized openings that won't leave buildings overheating in summer

GUEST:

Ben Jones

Associate Professor, University of Nottingham | Lead Author, CIBSE AM10

https://www.linkedin.com/in/benjamin-jones-0686a214/

CIBSE AM10: Natural Ventilation in Non-Domestic Buildings

https://www.cibse.org/knowledge-research/knowledge-portal/am10-natural-ventilation-in-non-domestic-buildings-2026-pdf/

The Air Quality Matters Podcast in Partnership with

Particles Plus https://particlesplus.com/

Lindab (https://www.lindab.ie/) - Eurovent (https://www.eurovent.eu/) - Aico (https://www.aico.co.uk/)

The One Take Podcast in Partnership with

SafeTraces (https://www.safetraces.com/) and Inbiot (https://www.inbiot.es/?utm_campaign=simon&utm_source=airqualitymatters&utm_medium=podcast)

Do check them out in the links and on the Air Quality Matters Website. (https://www.airqualitymatters.net/podcast)

If you haven't checked out the YouTube channel its here (https://www.youtube.com/@airqualitymatters-SimonJones). Do subscribe if you can, lots more content is coming soon.

Chapters

00:00:00 Introduction: The Return of Air Quality Matters
00:02:14 The Genesis of AM10: A 20-Year Evolution
00:06:03 From PhD to Practice: Ben's Natural Ventilation Journey
00:08:34 The Philosophy Behind AM10: Making Physics Accessible
00:10:14 Why Ventilate: Sizing for Summer, Surviving Winter
00:11:19 The Physics of Buoyancy: When Hot Air Actually Rises
00:13:09 When Design Meets Reality: The Complexity Challenge
00:14:41 The Feasibility Question: Is Natural Ventilation Right for Your Building?
00:15:48 The Neutral Pressure Level: Where Physics Flips Sign
00:16:50 Wind's Wild Card: Adding Complexity to Buoyancy
00:18:44 The Case for Natural Ventilation: Energy, Carbon, and Human Connection
00:19:17 The Adaptive Comfort Advantage: When Control Matters More Than Precision
00:23:19 Natural Ventilation Through the Ages: Ancient Wisdom Meets Modern Buildings
00:31:59 The Outdoor Air Reality: When Fresh Air Isn't Fresh
00:42:15 The Great Automation Failure: 3200 PPM in London's Smartest Building
00:35:04 What Changed in 2026: New Physics and Effective Area
00:39:25 From Spreadsheets to Software: How AM10 Gets Used
00:40:40 Designed for Everyone: Who Should Read AM10
00:42:40 The Sensor Revolution: Transparency in Natural Ventilation Performance
00:54:26 Hot Climate Solutions: Thermal Mass and Ancient Technologies
00:55:47 The Fundamental Design Principle: Natural Ventilation from Day One
00:56:43 Getting Your Hands on AM10: Access, Training, and the Future