Air Quality Matters

This week, we dive into a fascinating full scale experimental study published in the Journal of Indoor Environments titled Indoor Laundry Drying: Full Scale Determination of Water Emissions Rates and Impact on Thermal Comfort, to explore a question that fundamentally challenges how we think about energy efficiency advice: What if the single most common energy saving recommendation—drying clothes indoors instead of using a tumble dryer—is actually forcing us to turn up the heating and creating serious indoor air quality problems we've never properly quantified?

Across Europe, particularly during winter months, over 60% of laundries are dried indoors in countries like Poland, Hungary, Czech Republic, and Finland. In France alone, tumble dryers account for 20% of average annual household electricity consumption. The advice is clear: save energy, ditch the dryer, hang your clothes on a rack. But while we know this practice coincides with dust mite growth and high concentrations of airborne mould spores due to rising moisture, the actual kinetics—how much water is emitted, exactly when, and how it physically changes the room's environment—has never been properly quantified in a controlled, full scale way. Until now.

Key Topics Discussed:

• The Cotton Culprit: A typical four kilogram load of dry cotton towels will hold about two litres of water after a standard 40 degree wash. Spinning faster than 1,000 RPM doesn't extract much more water. Cotton is the real moisture problem when it comes to indoor drying.
• Three Phases of Drying: By constantly weighing the drying rack and monitoring room humidity in a controlled 40 cubic metre experimental chamber, researchers discovered water emission isn't a slow, steady trickle. It happens in three distinct phases: the initial burst (first two hours, exceeding 100 grams per hour, peaking at 360 grams per hour), the steady state (10 to 25 hours, stabilizing around 50 grams per hour as the room becomes humid), and the exhaustion phase (beyond 30 hours, gradually tailing off).
• The Temperature Drop Problem: Evaporating water is endothermic—it literally sucks heat out of surrounding air. As laundry dried, room temperature dropped significantly, recording drops between half a degree and 3.8 degrees Celsius. If your room starts off quite dry, the initial humidity gradient is higher, water evaporates faster, and the temperature drop is even sharper.
• The Thermal Comfort Failure: When researchers mapped these temperature and humidity changes onto standard thermal comfort charts like ASHRAE 55, the results were clear: passive indoor laundry drying actively drags room conditions right out of acceptable comfort zones. Even wearing thicker winter clothes only partially mitigates the discomfort.
• The Heating Paradox: If we're told to avoid tumble dryers to save energy, but doing so drops the temperature of our living spaces by almost four degrees, what do we inevitably do? We turn up the central heating. The energy saving advice creates a new energy consumption problem.
• Mitigation Strategies: We need to be strategic about where we dry clothes. Positioning drying racks in bathrooms close to air extraction points can avoid spreading moisture and physically cooling down living and sleeping spaces. The first hour or two of clothes drying is particularly critical for moisture emission.

Indoor laundry drying: Full-scale determination of water emission rate and impact on thermal comfort https://doi.org/10.1016/j.indenv.2025.100089

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.

• 00:00:00 Introduction: The One Take Format and the Mundane Routine of Laundry
• 00:00:58 The Energy Paradox: Why We're Told to Ditch the Tumble Dryer
• 00:02:21 The Cotton Culprit: How Much Water Are We Really Releasing?
• 00:03:03 The Three Phases of Drying: From Burst to Exhaustion
• 00:04:04 The Endothermic Effect: Why Drying Clothes Literally Cools Your Room
• 00:04:40 The Thermal Comfort Crisis: When Laundry Drags You Out of the Comfort Zone
• 00:05:04 The Heating Trap: Trading Tumble Dryer Energy for Central Heating
• 00:05:26 The Strategic Solution: Building Physics Meets Laundry Day
• 00:06:01 Closing Thoughts: Treating Mundane Tasks with Building Physics Respect

This week, we sit down with Rachel Hodgdon, President and CEO of the International WELL Building Institute (IWBI), to explore a question that fundamentally challenges how we think about healthy buildings: What if the single biggest barrier to transforming the built environment isn't our lack of knowledge about indoor environmental quality—but our inability to communicate complexity in ways that inspire action rather than paralysis?

Key Topics Discussed:

• Meeting People Where They Are: How do you communicate the holistic vision of indoor environmental quality without overwhelming stakeholders? Rachel explains why IWBI always starts with what matters most to the person across the table. If you're talking to a CEO, lead with recruitment, retention, and productivity. If you're talking to a facilities manager, talk about deferred maintenance and occupant satisfaction.
• Incremental Progress Over Perfection: Unlike many certifications that reward only finished projects, WELL is designed to celebrate incremental progress. WELL at Scale has proven that clients don't move in straight lines. They might start with one landmark building, then progress toward equity ratings across portfolios, or spend a year focusing on just a few features. One point earned toward any designation now counts toward full certification.
• Performance Testing Reveals the Invisible: WELL is proudly performance based. After a project is complete and occupied, third party testers measure air quality, water quality, thermal comfort, lighting, and sound. Buildings that fail must retest. Rachel shares stories of projects that discovered elevator shafts pumping unfiltered air into lobbies, printers off gassing VOCs, and contaminated soil beneath indoor plants. Without performance testing, these issues would never have been found.
• Residential and Affordable Housing: WELL for Residential launched as a pilot expecting 3,000 enrollments. It received 30,000 straight out of the gate, including 22,000 military homes. Rachel highlights a groundbreaking partnership with Enterprise Community Partners, embedding WELL into the Enterprise Green Communities standard for affordable housing. This means WELL is now legislated in over 50 percent of US states for affordable housing, ensuring the people most in need benefit first, not last.

GUEST:

Rachel Hodgdon

President and CEO, International WELL Building Institute

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

IWBI https://www.wellcertified.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.

• 00:00:00 Introduction: Meeting Rachel Hodgdon and the IWBI Mission
• 00:02:50 The Complexity Challenge: Communicating Holistic Indoor Environmental Quality
• 00:03:53 One WELL: Simplifying Entry Points and Rewarding Incremental Progress
• 00:07:59 The Apple Approach: Building a Unified Ecosystem for Healthy Buildings
• 00:09:40 Evolution from Green Buildings: The Second Wave of Sustainability
• 00:12:29 Authority and Accessibility: Balancing Technical Rigor with Broad Appeal
• 00:21:37 Meeting People Where They Are: The Art of Advocacy and Communication
• 00:31:47 The Power of Experience: Case Studies and Exemplar Spaces
• 00:36:05 Beyond Headquarters: Reaching the Long Tail of the Built Environment
• 00:39:27 WELL at Scale and Existing Buildings: Flexibility for Portfolios
• 00:40:58 Military Housing and Affordable Housing: 30,000 Homes and Counting
• 00:55:56 The Australian Success Story: What's Happening Down Under
• 00:58:54 Navigating Headwinds: DEI, Sustainability, and the Great Rebrand
• 01:05:05 Performance Testing and Accountability: Making the Invisible Visible
• 01:23:23 The ROI of Healthy Buildings: Retention, Recruitment, and Productivity
• 01:20:48 Neurodiversity and Universal Design: Designing for the Extremes Benefits Everyone
• 01:42:45 The Medical Gap: Why Doctors Don't Ask About Your Home
• 01:47:15 The Future: Continuous Monitoring and the Next Ten Years
• 01:50:33 Closing Thoughts: Data is Knowledge, Knowledge is Power

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.

• 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.

• 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.

• 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.

• 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.

• 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

This week, we sit down with Danny Ashton, founder and host of HouseFresh, a consumer comparisons and testing YouTube channel and website for residential air cleaners, to explore a question that fundamentally challenges how we buy, trust, and understand indoor air quality technology: What if the air cleaner market is deliberately designed to confuse you—and what if the only way to cut through the noise is to test everything, measure what matters, and refuse to play the game?

Danny brings a rare combination of technical rigour, marketing insight, and consumer advocacy to a sector that desperately needs it. Since 2020, he has tested over 130 air cleaners in real-world conditions, measuring particulate removal performance, sound levels, energy consumption, and filter costs—creating one of the most valuable independent resources available to consumers today.

Key Topics Discussed:

• The 2020 Fog of War: What it was like looking out at the air cleaner landscape during the pandemic. A marketplace flooded with products from every corner of the planet, tested in different ways, presenting benefits in wildly inconsistent formats. An unbelievable minefield for consumers desperate to protect their families.
• The Invisible Product Problem: Why air cleaners are uniquely vulnerable to being sold poorly. You can tell if an air fryer doesn't work. You can't see particulate matter. A product could be absolutely rubbish and you'd have no idea. That opens the door for companies to sell what sells, not what works.
• The Affiliate Revenue Trap: How the entire online ecosystem is rigged around pushing products that pay the highest commissions, not the ones that perform best. Some models offer 40 to 50 percent affiliate cuts versus 2 or 3 percent for others. The incentive structure is broken, and consumers pay the price.
• What Actually Matters: Performance at quiet fan speeds, not just top speed. Energy consumption over time. Filter replacement costs. Sound quality, not just decibel ratings. The ability to turn off ionizers, UV lights, and other additive technologies. The fundamentals that marketing doesn't want you to focus on.
• The PC Fan Revolution: Why DIY air cleaners built with computer fans and standard filters consistently outperform expensive retail units on performance, noise, and cost. Clean Air Kits, New Care, Nukit—small teams delivering serious engineering without the marketing budget or the proprietary filter lock-in.
• The Carbon Filter Lie: How thin fabric carbon layers smell sweet for a few weeks and then fail completely, triggering consumers to replace entire filter assemblies. Meanwhile, thick bonded carbon filters can last significantly longer—but they cost more and don't drive repeat sales as aggressively.

GUEST:

Danny Ashton

Founder and Host, HouseFresh

Danny Ashton LinkedIn - https://www.linkedin.com/in/dannyashton/

https://housefresh.com/

https://www.youtube.com/@HouseFresh

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.

• 00:00:00 Introduction: The Invisible Problem with Air Purifiers
• 00:02:41 The Fog of War: Air Quality During the Pandemic
• 00:03:18 Learning from the Past: The 2010s Air Purifier Landscape
• 00:06:06 The Bamboozle Business: How Confusion Sells Products
• 00:08:07 The Testing Philosophy: Benchmarking What Actually Matters
• 00:09:37 The Sound and the Fury: Why Quiet Performance Matters Most
• 00:12:03 The Amazon Hellscape: Peak Online Shopping Meets Air Quality
• 00:13:38 The Air Fryer Test: Why Air Purifiers Are Uniquely Deceptive
• 00:29:23 The Great Filter Debate: HEPA Hype vs Real World Performance
• 00:27:12 The PC Fan Revolution: When Computer Nerds Met Air Quality
• 00:34:24 The Razor Blade Business Model: Filters as Recurring Revenue
• 00:37:26 The Size Problem: Why Bigger Really Is Better
• 00:54:30 The Sensor Gimmick or Game Changer Question
• 01:07:05 The Carbon Conundrum: When Filters Fight Odors and Lose
• 01:16:42 The Additive Air Cleaner Minefield: Ionizers, UV, and Chemistry
• 01:27:06 The Testing Reality: 133 Units and Counting
• 01:44:22 The YouTube Education Effect: Maturing the Consumer Market
• 01:37:25 The Future: Matter Protocol and Smart Home Integration
• 01:50:06 The Mission: Raising the Bar in a Rigged Market

This week, we step slightly outside the building envelope to examine a question that fundamentally challenges everything we think we know about air pollution: What if the metric the entire world uses to measure air quality is structurally blind to the most dangerous particles we breathe?

The document is a perspective piece published in the Bulletin of the World Health Organization, titled Air Quality Standards and WHO Guidance on Particulate Matter Measurement 2.5 Microns. It represents a profound wake-up call for the global air quality community, arguing that PM 2.5—the gold standard metric used worldwide to regulate, monitor, and discuss particulate air pollution—has serious fundamental blind spots that could be undermining decades of public health policy.

The World Health Organization's normative guidance on ambient air quality is fundamentally based on evidence from health and exposure studies regarding the harms associated with mass concentrations of airborne particulate matter expressed as PM 2.5. These WHO guidelines are a critical reference point for jurisdictions all over the planet when developing or revising their own ambient air quality standards. But this paper makes a stark argument: our global gold standard is missing the full scope of health-harming particulate air pollution.

Key Topics Discussed:

• The Harmonization Problem: The current WHO guidance does not cover harmonization of averaging methods for concentrations measured during data aggregation, nor does it cover how to handle exceedances of PM 2.5 levels. Variations in how different countries measure and aggregate data can obscure true ambient air pollution levels—comparing apples with oranges on a global scale.
• The Mass-Based Metric is Fundamentally Flawed: PM 2.5 is a mass-based metric. It simply weighs the dust. It completely fails to consider the physicochemical characteristics of airborne particles—their specific size, chemical composition, bioavailability of potentially harmful elements, and critically, the particle number concentrations of different sized particles, including ultrafine particles.
• The Bowling Ball vs. Marbles Problem: Imagine a box. A single bowling ball gives you a high weight reading. But what if that box is filled with tens of thousands of marbles? The mass of PM 2.5 comes mostly from larger fine particles. The mass of ultrafine particles is negligible when compared to bigger particles. However, the vast majority of particles in typical ambient environments are ultrafine particles—defined as being less than 0.1 microns. A city could hit its WHO mass targets by removing a few heavy bowling balls but leave tens of thousands of smaller marbles floating around.
• The 5 Microgram Threshold: When PM 2.5 is higher than 5 micrograms per cubic meter, the mass concentration does not correlate well with the particle number of ultrafine particles. Therefore, control measures that aim to reduce high PM 2.5 levels might not actually reduce the ultrafine particle count at all. A good correlation does exist below 5 micrograms per cubic meter, but as the authors bluntly state, most countries are far from achieving such low ambient air pollution.
• Why Ultrafine Particles Are So Dangerous: Because they are so small, they don't just get stuck in your throat or upper airways—they go deep. Short-term exposure is associated with respiratory symptoms and systemic inflammation, affecting your heart and blood pressure. Long-term exposure is associated with increased mortality, especially cardiovascular and lung-related mortality, as well as ischemic heart disease.

Air Quality Standards and WHO Guidance on Particulate Matter Measurement 2.5 Microns

Bulletin of the World Health Organization 10.2471/BLT.23.290522 (https://doi.org/10.2471/BLT.23.290522)

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)

• 00:00:00 Introduction: The Blind Spot in Our Global Air Quality Standard
• 00:01:49 The Structural Problem: Missing Harmonization in WHO Guidance
• 00:02:45 The Fundamental Flaw: Why Mass-Based Metrics Miss the Point
• 00:03:49 The Bowling Ball vs Marbles Problem: Understanding Particle Count
• 00:05:14 The Five Microgram Threshold: Where Mass and Number Diverge
• 00:06:18 The Health Threat: Why Ultrafine Particles Are So Dangerous
• 00:07:13 The Solution: Introducing PM 2.5 Number Density Metric
• 00:08:33 The Practical Challenges: Monitoring Ultrafine Particles in the Real World
• 00:09:32 The Indoor Air Quality Wake-Up Call: What Your Monitors Are Missing
• 00:11:20 The Path Forward: Harmonizing Global Standards for Real Protection

This week, we sit down with Jason Jones, Director of Air Quality Management at Fellowes, to explore a question that fundamentally challenges how we sell, specify, and sustain indoor air quality solutions in the real world: What if the biggest barrier to clean indoor air isn't technology or science—but the economic conversation we're having with the people who actually have to write the cheques?

Jason leads Fellowes' sales and marketing efforts in the air quality space, working closely with distributors, sales representatives, and end users to help them understand the role of smart, responsive air quality management. This is a theory into practice conversation, and it's critically important. We can discuss the impacts of air quality on health, wellbeing, performance, and energy all day long—but at some point, someone, somewhere, has to literally buy into the idea. Jason provides a fascinating window into how a respected player in the sector, delivering products that actually improve air quality, frames the problem and the solutions, how those conversations are going, and where they think this sector is heading next.

Key Topics Discussed:

• Post-Pandemic Reality: How air quality awareness has evolved since COVID. Some people internalized the lesson and carried it forward into the environments they work in. Others were willing to just get back to normal. The perception problem: if it doesn't smell bad, chances are the air must be clean. But we don't get to control the air we breathe in most of the spaces we're in.
• Where the Traction Is: Healthcare, education, K-12, higher ed, and assisted living facilities are where air quality is sticking most. The generation that missed prom because of the pandemic took that lesson forward into their lives. That's why there's a bright future for air quality—it made an indelible mark on that generation.
• Leaning Into Energy Savings: Why Fellowes is talking more and more about energy savings and using standards like ASHRAE's Indoor Air Quality Procedure to specify air purification alongside HVAC systems. The goal: reach the same or better air quality while reducing outside air reliance. Clean air is a human right, but the reality is that building owners have bills to pay and balance sheets to worry about.
• VRP vs IAQP—A 101: Ventilation Rate Procedure is the blunt instrument—prescriptive ventilation rates based on building type and occupancy. Indoor Air Quality Procedure is more sophisticated—designing around specific contaminants of concern, factoring in air purification and filtration, and allowing you to reduce outside air by 30, 40, 50 percent or more. Less outside air means less heating and cooling, smaller HVAC systems, and potential first cost savings.
• The Education Experiment: Schools are a massive data set. With thousands of classrooms being phased into air quality solutions over time, we'll finally be able to see clear trends in absenteeism rates, teacher sick days, and student test scores. You can't learn if you're not in class. It's that simple. And it's the most black and white metric of them all.

GUEST:

Jason Jones https://www.linkedin.com/in/jason-jones-0aa672b/

Director of Air Quality Management, Fellowes

Fellowes https://www.fellowes.com/

The Air Quality Matters Podcast in Partnership with

Particles Plus https://particlesplus.com/

Farmwood (https://farmwood.co.uk/) - Eurovent (https://www.eurovent.eu/) - Aico (https://www.aico.co.uk/) - Ultra Protect (https://www.ultra-protect.co.uk/air-quality-matters)

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.

• 00:00:00 Introduction: The Commercial Reality of Indoor Air Quality
• 00:03:11 Post-Pandemic Reality: Who Still Cares About Air Quality?
• 00:08:09 The Budget Battle: Nice to Have vs Need to Have
• 00:10:05 The Energy Efficiency Angle: A New Way to Sell Clean Air
• 00:26:00 VRP vs IAQP: Two Approaches to Building Ventilation
• 00:24:47 The HVAC Energy Equation: Why Outside Air Is So Expensive
• 00:34:18 The Complexity Challenge: Is the Industry Ready for IAQP?
• 00:37:51 The Subjective Element: Why Human Perception Still Matters
• 01:25:09 The Fellows Ecosystem: Networked Air Quality Management
• 01:16:44 Education as the Testing Ground: The Data Goldmine
• 01:41:28 The AI Revolution: Natural Language Control of Building Systems