Air Quality Matters

This week, we sit down with José Luis Gutiérrez Villanueva, a specialist radon measurement advisor at Radanova, member of the Commission on Radon Communication at the Spanish Professional Association of Physicists, and deeply involved in standards across Europe, to explore a question that fundamentally challenges how we think about indoor air quality and radiation protection: What if the single biggest barrier to protecting people from radon exposure isn't our lack of scientific knowledge or technology—but our complete failure to recognise that the only way to know your radon level is by measuring it, that no two buildings are the same, and that the invisible nature of this radioactive gas means millions of people are unknowingly breathing air that significantly increases their risk of lung cancer every single day?

Key Topics Discussed:

• The European Directive That Changed Everything: Since 2014, when the new European Directive on Radiation Protection was approved, all 27 member states now have legislation in place with reference levels for radon. For the first time in the history of radiation protection in Europe, every country must have a number in their national legislation. This is a massive game changer. Before that, there were only recommendations. Some countries followed them, others did not. Now there is a legally binding reference level, and this has moved everything forward.
• What Is Radon and Why Does It Matter: Radon is a naturally occurring radioactive noble gas that comes from the decay of uranium in soil and rock. It is everywhere. Outdoors, levels are usually very low, but indoors, radon can accumulate to dangerous concentrations. When you breathe radon, the gas itself is inert and exhaled, but during its journey through your lungs, radon decays into radioactive polonium, which attaches to lung tissue and emits alpha particles. These alpha particles have enough energy to damage DNA, and over years of continuous exposure, this damage accumulates and significantly increases the risk of lung cancer. After smoking, radon is the second leading cause of lung cancer.
• How Passive Radon Detectors Work: Passive radon detectors use a special plastic called CR39 inside a holder. Radon gas diffuses into the holder, and when radon decays, it emits alpha particles that create microscopic tracks in the plastic. After exposure, the detector is returned to the lab where the plastic undergoes chemical etching. The etching process enlarges the tracks so they can be counted under a microscope. The lab counts the number of tracks per square millimetre, applies a calibration factor, and calculates the radon exposure. This is then divided by the exposure time to give a result in becquerels per cubic metre.
• Why You Cannot Predict Radon Without Measuring: You cannot compare your home with your neighbour's home. Even if you live in detached houses next to each other, your radon levels can be completely different. Radon levels can vary dramatically within the same property, from room to room, and over time. Weather, soil moisture, air pressure, ventilation, and building characteristics all affect radon. One home on top of a hill might see radon drop when it rains, while a home in the valley below sees radon increase. Radon levels can fluctuate by more than 50 percent from year to year. The only way to know your radon level is by testing.

GUEST:

José Luis Gutiérrez Villanueva

Specialist Radon Measurement Advisor, Radanova

https://www.linkedin.com/in/joseluis-gutierrez-radonspecialist/

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This week, we dive into a groundbreaking study published in The Lancet Public Health titled Impact of Ultra Low Emission Zone on Lung Function Growth in Children in London: A Prospective Parallel Cohort Study, to explore a question that fundamentally challenges how we think about air pollution and child health: What if the single biggest barrier to protecting our children's respiratory health isn't our lack of scientific knowledge or technology—but our complete failure to recognise that when we clean up urban air pollution, children's developing lungs don't just stop getting worse, they actually catch up, proving that early life deficits can be restored and that clean air zones are not just environmental policy, but direct biological interventions with immediate, measurable health benefits?

Key Topics Discussed:

• The Scale and Methodology: A Masterclass in Longitudinal Research: Known as the CHIL study, the Children's Health in London and Luton study, this was a prospective parallel cohort study. The researchers approached 122 primary schools and an impressive 69 percent agreed to participate. They recruited a massive cohort of 3,414 children aged six to nine years old. They followed these kids over four to five year periods, performing annual spirometry tests right in the school to measure FEV1, forced expiratory volume in one second, and FVC, forced vital capacity. They coupled these clinical tests with high resolution dispersion modelling to estimate annual air pollution exposure at each child's home address. This is rigorous, large scale, longitudinal public health research at its finest.
• Complete Recovery: The Gap Was Closed: Then London implemented the ULEZ and over the follow up period the researchers watched a dramatic shift occur. The children in London saw their FEV1 growth increase by an extra 10 millilitres per year compared to the children in Luton. Because of that accelerated growth, after just four years of follow up, the children in London did something many experts thought was impossible. They reached complete parity with Luton. The gap was completely closed. Even more astonishing, the proportion of children in London with clinically impaired lung function fell from 14 percent at baseline down to just 9 percent by the end of the study. The introduction of the London ULEZ was associated with improved lung function growth trajectories, suggesting that previous deficits in lung development were restored.
• The Built Environment Connection: Historically, we have often treated building ventilation and outdoor air quality as two entirely separate silos. But this paper proves that they are intimately connected. Outdoor air is the raw intake for our indoor environments. By implementing clean air zones like the ULEZ, we are performing a massive city scale pre filtration of our indoor air. If we can close a 38 millilitre lung deficit and restore clinical impairment just by cleaning up the ambient city streets, we are proving that environmental interventions have an almost immediate direct biological benefit. If cleaning up outdoor air can do this, imagine the health optimisation we can achieve if we combine ambient clean air zones with high quality filtered and mechanically ventilated indoor spaces. We spend 90 percent of our lives indoors after all.

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Charity Partner - https://www.saferairproject.org/

This week, we sit down with Brian Renda, Programme Director for the Built Environment, and Victoria Slaughter, PPE Director at Blueprint Biosecurity, to explore a question that fundamentally challenges how we think about pandemic preparedness: What if the single biggest barrier to preventing the next pandemic isn't our lack of scientific knowledge or technology—but our complete failure to recognise that preparing for respiratory pandemics requires pathogen agnostic infrastructure deployed before emergencies strike, high quality respirators accessible to everyone who needs them, and a fundamental shift from accepting pandemics as inevitable to building systems where outbreaks are contained before they spiral into global catastrophe?

Key Topics Discussed:

• Post COVID Reality and the Challenge of Sustained Preparedness: It is incredibly hard to plan and respond to threats that are not immediately in front of you. During the pandemic, the risk was visible and destructive. Now that attention has shifted, it is difficult to maintain focus on the next pandemic when we do not know if it will happen in one year, ten years, or a hundred years. Blueprint's role is to advance our overall state of readiness so that while we may not be able to stop outbreaks from happening, we can stop them from progressing into pandemics. History has shown we cannot predict when the next large event will be. We must be in preparation mode, but we cannot assume we have infinite time. The earlier preparations are done, the better protected we are.
• The Mask Versus Respirator Problem: So much of the confusion and misinformation during COVID stemmed from a lack of access to high quality products. There is an enormous difference between a mask and a respirator. A respirator filters the air a user breathes to a regulatory standard such as N95 or FFP3. A surgical mask or cloth mask does not. Surgical masks are designed to catch large particles and spit from a wearer's mouth in sterile environments. They are not designed to filter aerosols or airborne particles. The lack of any standard for cloth masks meant protection was wildly variable. Some offered almost no protection at all. When people are given high quality respirators with known efficacy, they do not have to wonder if something is protecting them. That changes everything.
• Stockpiling Strategy and the Lessons from COVID Waste: Respirators do expire, but the standards are extraordinarily high because these products are a person's last line of defense. Most respirators last longer than their expiration date, but manufacturers want to ensure even the final 0.1 percent that may no longer be good does not reach a person. Some respirators have shelf lives upwards of 20 years. That is very different from products that expire every three years. Smart stockpiling means filling warehouses with products that are ideal for long term storage and allowing for product rotation. Post COVID, many stockpiles are starting to disappear simply because products are expiring.
• The Built Environment Programme and Pathogen Agnostic Technologies: Blueprint focuses on interventions that are pathogen agnostic, work in occupied spaces, have promising safety and efficacy profiles, integrate into current operations without major disruption, and have the potential to be cost effective. Their formal programmes include Far UVC at 222 nanometers, which has much higher exposure limits than conventional 254 nanometer UVC because of its shorter penetration depth. Conventional upper room GUV, which has been studied since the 1930s yet is still barely used. And glycol vapors such as propylene glycol and triethylene glycol, which have been shown to deactivate aerosolized pathogens and are already mass manufactured for industrial processes. These could be deployed during emergencies with emitters in homes or businesses to add air treatment capacity with relatively little cost or infrastructure.

Brian Renda https://www.linkedin.com/in/brian-renda-4264132/

Victoria Slaughter https://www.linkedin.com/in/victoriaslaughter/

Blueprint Biosecurity https://blueprintbiosecurity.org/

• The Air Quality Matters Podcast in Partnership with
  
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This week, we dive into a study published in Atmospheric Pollution Research titled Effects of Classroom Ventilation Management and User Activities on Indoor Air Quality in Madrid Primary Schools: A Two Year Field Study, to explore a question that fundamentally challenges how we think about school environments and indoor air quality: What if the single biggest barrier to delivering healthy classroom air isn't our lack of scientific knowledge or technology—but our complete failure to recognise that asking teachers to be human HVAC controllers, manually managing windows while teaching 30 active children in densely packed spaces, is a fragile, unstable and fundamentally unsustainable way to manage a building?

Key Topics Discussed:

• The Research Design: A Two Year Behavioral Intervention Study: This Madrid study wanted to see if we could solve this problem through behavioral management alone. They set up a two year field study monitoring nine classrooms across four primary schools. During the first year, they just watched. They recorded business as usual, teachers and students opening and closing windows and doors completely freely based on whether they felt hot, cold or stuffy. Then in the second year, they intervened. They implemented a structured seasonal adapted manual ventilation protocol in one classroom per school, using the other classrooms as controls. This protocol was highly detailed. It scheduled specific window and door openings, such as five minutes at the start of the classroom, during every recess and during lunch breaks. And it adapted the width of the window opening based on whether it was freezing winter, mid season or a warm spring afternoon.
  
  
• The Human Factor: When Compliance Breaks Down: The biggest weakness of all is the human factor. A manual ventilation protocol is only as good as the people executing it. Compliance was highly erratic. In the dead of winter, teachers simply refused to open the windows because the cold drafts were unbearable. During exams or quiet study periods, windows stayed closed because the outdoor street noise was too distracting. If a teacher was in the middle of a complex, engaging lesson, they forgot about the protocol entirely. We are essentially asking teachers to be human HVAC controllers, managing drafts, noise, security and air quality, all while trying to teach 30 young children. It is a fragile, unstable and unsustainable way to manage a building.
• The Carbon Dioxide Results: Alarming Spikes and Protocol Limits: During lessons with closed windows, CO2 built up at an alarming rate, frequently soaring well past 1500 parts per million and even 2000 parts per million within 30 minutes. When the scheduled breaks arrived and the windows were opened, levels dropped rapidly. Did the structured protocol help? Yes, it did. The intervention classrooms had generally lower average CO2 levels than the business as usual classrooms. But even with strict compliance, they still recorded major CO2 spikes during long, densely occupied teaching blocks. It proved that in high density classrooms, manual natural ventilation simply cannot keep up. Passive window opening has physical limits, especially when wind speeds are low

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This week, we sit down with Amanda Reddy, Executive Director at the National Centre for Healthy Housing, to explore a question that fundamentally challenges how we think about housing quality and public health: What if the single biggest barrier to transforming housing quality isn't our lack of scientific knowledge or technology—but our complete failure to recognise that the places where we spend 70 percent of our lives, our homes, are either actively supporting or systematically undermining our health, and that fixing housing for the most vulnerable fixes it for everyone?

Key Topics Discussed:

• Lead Is Not a Solved Problem: Half a million children in the United States are still exposed to lead levels that threaten their ability to learn and thrive every year. Lead affects neurodevelopment, lowers IQ, impairs executive function and increases the risk of conduct disorders. But it also affects adults. A World Bank study estimated that lead exposure causes five and a half million deaths globally each year, more than AIDS, malaria and road traffic deaths combined. The amount of lead required to poison a child is invisible. Imagine a sugar packet of lead contaminated dust spread evenly over an American football field. That is still enough to be hazardous. You cannot clean your way out of this problem. You have to eliminate the source.
• The Three Pillar Strategy: The National Centre for Healthy Housing operates through research, policy advocacy and community capacity building. They identify what works through rigorous evidence, advance those solutions through federal, state and local policy changes, and then support communities to implement those solutions on the ground. But they do not arrive with predetermined answers. Communities own the bus. They decide where they are going, how fast and what route to take. The Centre brings expertise, tools and evidence to help navigate barriers, but the solutions are shaped by the people who live the experience every day.
• Climate, Housing and Health Collide: Extreme heat now affects 70 percent of Americans. Housing is central to how communities weather climate events, whether heat, cold, hurricanes or wildfires. But much of the existing housing stock was not built for the climate we are experiencing today, let alone the climate we will face in 2050. Seventy percent of the homes that will exist in 2050 are already built. Energy efficiency retrofits that sealed homes to save energy are now trapping heat. Communities are calling for a right to cooled air as part of habitability, just as heating became a requirement a century ago. But air conditioning every home is not the answer. Refuge spaces, community cooling centres, heat island mitigation and building design all have a role. The challenge is ensuring climate solutions do not fall disproportionately on low income residents who contributed least to the problem.
• Military Housing and Cultural Barriers: Over the past decade, military families have raised serious concerns about housing conditions. Mould, water damage, lead and poor maintenance are widespread. Military families face unique cultural pressures that make it difficult to report problems or advocate for repairs. Fear of repercussions for service members creates a chilling effect. Yet the cost of inaction is profound. A service member worried about their family's safety at home is a readiness issue.

GUEST:

Amanda Reddy

Executive Director, National Centre for Healthy Housing

https://nchh.org/

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This week, we dive into a study published in Building and Environment titled The Impact of Energy Retrofit on Indoor Air Quality in Classrooms and Offices, to explore a question that fundamentally challenges how we think about building performance and climate action: What if the single biggest barrier to decarbonising our building stock isn't our lack of technology or ambition—but our complete failure to recognise that when we tighten buildings to save energy, we risk sealing in pollutants, moisture and carbon dioxide, turning our classrooms and offices into actively harmful environments unless we treat mechanical ventilation as an absolute physical necessity, not an optional luxury?

Buildings in Europe are responsible for about 40 percent of our total energy consumption. If we are going to meet our climate and decarbonisation goals, we have to retrofit our existing building stock. There is no way around it. But there is a massive fear in our industry, and we have seen it happen time and time again, that when we tighten up these buildings to stop heat loss, we end up destroying indoor air quality. This Irish study is important because it did a rigorous pre and post retrofit evaluation of over 50 classrooms and offices, measuring CO2, fine particulate matter, nitrogen dioxide, temperature, humidity and a whole suite of volatile organic compounds.

Key Topics Discussed:

• The One Week Snapshot Problem: The biggest methodological limitation is that the monitoring campaigns are only one week long per phase. A week is just a snapshot in time. It does not capture seasonal variations. If the pre retrofit monitoring happened during a mild windy week in autumn when the windows were open and the post retrofit monitoring happened during a freezing calm winter day with everything shut down tight, the weather and teacher behaviour would heavily skew the results. A classroom environment is highly dynamic. The number of students, the specific lessons being taught, and even the type of cleaning products being used can vary wildly from one week to the next. This is a critical limitation that must be acknowledged when interpreting the results.
• The VOC Wildcard: The study noted that while ventilation improved overall, the response of volatile organic compounds was highly variable across different buildings. Why? Because energy retrofits introduce new synthetic materials into the built environment. New insulation, new sealants, new paints and sometimes new carpets and furniture. These materials off gas chemical compounds leading to short term spikes in total VOCs, even when the overall ventilation rate is technically higher. This is a critical warning to our industry. We cannot just focus on the ventilation rate. We must also practice strict source control by selecting low emitting natural materials during retrofits where we can or perhaps increase ventilation rates in the early stages of habitation of these spaces.
• The Carbon Dioxide Victory: Carbon dioxide concentrations in the retrofitted classrooms actually reduced by an average of 28 percent. That is a massive improvement. And why did this happen? It happened because the retrofits did not just focus on insulation and air tightness. They actively integrated mechanical ventilation with heat recovery.
• The Particulate Matter Win: PM2.5 levels decreased by 27 to 30 percent in both classrooms and offices. Before the retrofits, the buildings exceeded the WHO daily average guidelines for PM2.5 on 48 percent of the monitored days. After the retrofit, that number dropped to 26 percent. This is a huge public health victory, likely driven by the high efficiency filtration systems in the new mechanical ventilation units and tighter building envelopes keeping outdoor traffic pollution from leaking in.

The Impact of Energy Retrofit on Indoor Air Quality in Classrooms and Offices

10.1016/j.buildenv.2026.114963 (https://doi.org/10.1016/j.buildenv.2026.114963)

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This week, we sit down with Dennis Naughton, former Member of Parliament and Minister for Communications, Energy and Natural Resources in Ireland, to explore a question that fundamentally challenges how we think about science, policy and political decision making: What if the biggest barrier to transforming our built environment isn't our lack of scientific knowledge or technology—but our complete failure to recognise that the people who make policy decisions operate in a completely different world from researchers, and unless we learn to speak their language, translate evidence into clear actionable asks, and understand the brutal political realities they face, even the most overwhelming evidence will never make it through the door?

Dennis brings a rare and fascinating perspective. He comes from science, having worked in food microbiology research, before spending over 28 years in Parliament. As a former Minister, he worked at the point where evidence, politics, public policy and implementation meet.

Key Topics Discussed:

• The Three Audiences Problem: As a scientist, you are trained to communicate evidence to peers so they can repeat your study. As a politician, you have three completely different audiences. First, you have to convince your cabinet colleagues that this is a good idea, because if you don't have a majority, your proposal is dead. Second, you have to convince the finance ministry, because most policy changes have a financial cost. Third, you have to convince the public that this is worth doing. Researchers often present to policymakers as if they are speaking to technical experts. The evidence goes way over their heads. The facts don't change, but how you frame them must.
• The Blank Page Reality: One of the hardest decisions any minister can make is a decision with a blank page in front of you, with no evidence and no base whatsoever. Even partial evidence, even evidence with caveats, is infinitely better than nothing. When politicians work off a blank page, they go back to ideology. If the research community can provide even incomplete evidence, it gives policymakers a framework to start. But here's the reality. Politicians don't make evidence-based decisions. They make evidence-informed decisions. There are economic, social, cultural and political factors that must be weighed. Evidence is critical, but it's not the only input.
• The Six Question Framework: Every researcher needs to be able to answer six questions if they want policy impact. What is the problem you are trying to solve? Why is it a problem? How are you proposing to solve it? What is the policy ask? What is the difference if that policy ask is delivered? What is the barrier to implementing that policy? If you can answer those six questions and frame them in the context of the three C's, clarity, context and connection to people, you will have something powerful that resonates with both policymakers and decision makers.
• Political Capital is Finite: Politics is a rough business. You only have a certain amount of political capital. If you use it up on the wrong proposals, you are not heard. Worse, if you push something through cabinet and it fails in Parliament, or if it passes Parliament but the public revolts, you have burned capital and damaged your reputation. Every proposal a minister brings forward, they are putting their name, their reputation and their career on the line. That is why timing, framing and understanding the political landscape is everything. Ministers only bring proposals to cabinet when they know they will get approval. The skill is in reading the room, building the coalitions and presenting the case in a way that lands with peers, with finance and with the public.

GUEST:

Dennis Naughten

https://www.linkedin.com/in/denis-naughten-77231112/

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This week, we dive into a landmark policy paper published in Building and Environment titled Integrating Health and Indoor Air Quality into European Building Policy: A Landmark Policy Shift, to explore a question that fundamentally challenges how we think about building performance and public health: What if the single biggest barrier to transforming our built environment isn't our lack of scientific knowledge or technology—but our complete failure to recognise that the very directive designed to decarbonise European buildings has, for decades, systematically ignored the health of the people breathing the air inside them, until now?

Key Topics Discussed:

• The Directive Versus Regulation Problem: The biggest weakness of the EPBD recast is that it is a directive, not a regulation. The European Union cannot dictate exact binding indoor air quality numbers or ventilation rates. It is up to each of the 27 member states to write these requirements into their own national laws and building codes by May 2026. This is where the real danger lies. We are at risk of a heavily fragmented European market. Some progressive countries might adopt strict health-based limits, while others, concerned about short-term compliance costs for developers, might do the absolute bare minimum. A race to the bottom.
• The Paper Compliance Risk: There is a major risk of paper compliance, where buildings are designed and certified to meet high indoor environmental quality standards on paper, but in reality, the ventilation systems are turned off, uncommissioned, or poorly maintained once the occupants move in. Many member states simply do not have the technical infrastructure, the trained inspectors, or the enforcement mechanisms to monitor indoor environmental quality on an ongoing basis. Without strict enforcement and penalties, these new laws risk becoming toothless tigers.
• The RHEVA Model: To combat fragmentation, the authors make a strong call to action for member states to adopt a harmonised, health-based framework. They point to the REVA model, Indoor Environmental Quality Regulation, as the gold standard, ready-to-adopt framework. REVA recommends continuous monitoring of two key parameters: PM2.5 and CO2. PM2.5 is a direct measure of exposure to fine particulate matter, which has devastating long-term health consequences. CO2 serves as a real-time proxy for overall ventilation adequacy and airborne infection risk.
• Countries Leading the Way: Belgium has a history of air quality legislation dating back to 1946. In 2022, they passed a comprehensive law that treats indoor air quality in public spaces as a right-to-know issue, requiring monitoring, certification and public labelling. France is also leading by requiring indoor air quality monitoring in schools and nurseries to protect sensitive populations. These examples prove that robust, enforceable indoor air quality legislation is not only possible, but already happening.

Integrating health and indoor air quality into European building policy: A landmark policy shift

Building and Environment

https://doi.org/10.1016/j.buildenv.2026.114508

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This week, we sit down with Plum Stone, founder and CEO of the Safer Air Project, to explore a question that fundamentally challenges how we think about indoor air quality and accessibility: What if the single biggest barrier to transforming indoor air quality isn't our lack of scientific knowledge or technology—but our complete failure to recognise that millions of people living with chronic health conditions face invisible barriers to accessing public spaces every single day, and that fixing air quality for the most vulnerable fixes it for everyone

Key Topics Discussed:

• The Lived Experience of Poor Air Quality: For people living with chronic health conditions, poor air quality is not an abstract future risk. It is a daily, immediate barrier to participation in public life. For someone with a compromised immune system, an underventilated classroom or meeting room can mean a week of illness, hospitalisation, or worse. For their families, it means constant vigilance, isolation, and the burden of protecting themselves when policymakers and building operators fail to act. This is not just a health issue. It is an accessibility issue. And yet, unlike wheelchair ramps or hearing loops, air quality remains invisible, unregulated, and largely ignored.
• Prevention as the Biggest Lever: Whilst the Safer Air Project started by advocating for people with existing chronic health conditions, Plum has come to see air quality as the single biggest lever we have to prevent chronic disease in the first place. Cardiovascular disease, stroke, dementia, asthma, and long term respiratory conditions are all driven by exposure to poor air quality. If we can push down on air pollution and airborne infection transmission, we give ourselves a real head start on prevention. This is not just about protecting the vulnerable. It is about reducing the growing burden of chronic disease on society and freeing up resources to invest in health, not just treat illness.
• Making the Invisible Visible: The first step to solving any problem is measuring it. The Safer Air Project is running a global campaign called Making the Invisible Visible, asking organisations to monitor air quality in public spaces and display that information transparently. If you are not measuring it, you are not managing it. And if you are not making it visible, people cannot make informed decisions about their safety. The campaign is simple. Monitor your air quality. Display your air quality. Commit to transparency. This is not just about CO2 numbers. It is about giving people the information they need to assess risk in real time, whether that is a vulnerable person deciding whether to enter a space, or a facilities manager realising their ventilation system is not performing as it should.
• The Role of Unions and Workplace Safety: Unions have been at the forefront of workplace safety for centuries, yet they have been almost entirely absent from the air quality conversation. That is starting to change. The Australian Council of Trade Unions has been a strong advocate, recognising that air quality is a workplace health and safety issue. Employers have a responsibility to provide safe working environments. That includes the air employees breathe. The new Model Code of Practice for the Control of Biological Hazards in the Workplace recognises biological hazards that transmit through the air. This is a huge step forward. But enforcement and implementation remain the challenge. Unions have the power to demand safe air for workers. And when you fix air quality for workers, you fix it for students, patients, and the public.

GUEST:

Plum Stone

Founder and CEO, Safer Air Project

https://www.saferairproject.org/

The Air Quality Matters Podcast in Partnership with

Mann + Hummel https://www.mann-hummel.com/en.html Particles Plus https://particlesplus.com/

Eurovent (https://www.eurovent.eu/) - Aico (https://www.aico.co.uk/) - Lindab (https://www.lindab.ie/) - S&P UK (https://www.solerpalau.com/en-uk/)

The One Take Podcast in Partnership with

SafeTraces (https://www.safetraces.com/) - Inbiot (https://www.inbiot.es/?utm_campaign=simon&utm_source=airqualitymatters&utm_medium=podcast) - Farmwood (https://farmwood.co.uk/) - iE Electronics (https://www.eielectronics.ie/) and iAir Group (https://iair-group.com/)

Zehnder https://www.zehndergroup.com/en

Charity Partner - https://www.saferairproject.org/

This week, we dive into a study published in Building and Environment titled A Scalable Framework for Impact Analysis of Faults on Indoor CO2 in Buildings, to explore a question that fundamentally challenges how we think about building maintenance and indoor air quality: What if the single biggest barrier to delivering healthy indoor environments isn't our lack of technology or standards—but our complete failure to recognise that the faults we routinely ignore in HVAC systems are actively degrading the air we breathe, and we've had no systematic way to prioritise which faults actually matter until now?

Key Topics Discussed:

• The Correlation Versus Causation Problem: In a building, everything is connected. If you just look at raw data, you might see counterintuitive things. For example, when the outdoor air damper is wide open, CO2 levels might actually be higher. A simple correlation analysis might conclude that opening the damper causes CO2 to rise, which makes no physical sense. What's actually happening is demand controlled ventilation. The system opens the damper because CO2 is rising. High CO2 is causing the damper to open, not the other way around. It's a classic feedback loop. To get around this simultaneity bias, the researchers used a clever approach called double machine learning. They stripped away all the noise and confounding variables like building ID, time of day, weather and current CO2 baseline, so they could isolate the true causal impact of a specific fault on CO2 levels.
• The Worst Faults for Air Quality: The absolute worst fault for indoor air quality is an AHU discharge fan failure. When the fan isn't generating the static pressure needed to move air, supply airflow drops off a cliff and return air CO2 spikes. The next worst is a poorly tuned system where the outside air damper is oscillating wildly, constantly cycling back to its closed position, severely reducing the overall volume of fresh air entering the building. Then there are valve leaks. A leaking cooling valve causes the supply air temperature to drop too low. The control system opens the heating valve and closes the outside air damper to keep warm air in. Because of a leaking cooling valve, your fresh air intake gets choked off and indoor CO2 shoots up. A leaking heating valve does the opposite. It opens the outside air damper to take advantage of free cooling, which actually dilutes indoor CO2 and improves air quality, but at a massive energy penalty.
• Zone Level Faults: At the zone level, the worst fault is terminal unit airflow set point unreachable low. This is when the VAV box damper is stuck or there's a ductwork issue, and the actual airflow to the room is consistently lower than what the thermostat is asking for. You get localised underventilation and zone CO2 spikes dramatically because fresh air is simply not getting into the space.
• The Prioritisation Framework: In facility management, we are constantly bombarded with fault alerts. In a large building, you might have hundreds of alerts a day, and maintenance teams are almost always stretched thin. Without a way to prioritise those faults, you end up ignoring them or focusing only on the ones that trigger immediate comfort complaints. This paper provides an evidence-based, data-driven ranking that lets facilities teams prioritise maintenance actions based on their actual impact on both energy and indoor air quality.

A scalable framework for impact analysis of faults on indoor CO2 in buildings

https://doi.org/10.1016/j.buildenv.2026.114443

The Air Quality Matters Podcast

Mann + Hummel https://www.mann-hummel.com/en.html Particles Plus https://particlesplus.com/

Eurovent (https://www.eurovent.eu/) - Aico (https://www.aico.co.uk/) - Lindab (https://www.lindab.ie/) - S&P UK (https://www.solerpalau.com/en-uk/)

The One Take Podcast in Partnership with

SafeTraces (https://www.safetraces.com/) - Inbiot (https://www.inbiot.es/?utm_campaign=simon&utm_source=airqualitymatters&utm_medium=podcast) - Farmwood (https://farmwood.co.uk/) - iE Electronics (https://www.eielectronics.ie/) and iAir Group (https://iair-group.com/)

Zehnder https://www.zehndergroup.com/en

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

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