Air Quality Matters

This week, we dive into a fascinating study published in Railway Engineering Science titled Study on Air Quality Improvements in Train Compartments by Coordinating Exhaust of Multiple Air Outlets, to explore a question that fundamentally challenges how we think about ventilation in mass transit: What if the single biggest barrier to protecting passengers on high speed trains isn't our lack of technology—but our complete failure to recognise that static, one size fits all ventilation systems can never deliver both thermal comfort and effective infection control across changing seasons?

Key Topics Discussed:

The Physics of Human Thermal Plumes: Most modern trains pump fresh conditioned air in from vents in the ceiling. But where does that stale air go? Usually it's exhausted through vents down near the floor. This study used CFD modelling to look at what happens if we rethink that. What if we coordinate exhaust at both the top and the bottom of the carriage? Human bodies create thermal plumes. We are basically 100-watt heaters and warm air naturally rises off us, carrying our exhaled breath upwards. In the summer, when the air conditioning is trying to cool the cabin, if you exhaust the air entirely from the top of the carriage, like near the luggage racks, you are working with that natural thermal plume. The hot, polluted air rises off the passengers and gets sucked right out of the top vents. The study found this significantly improves the cooling efficacy and efficiency. You aren't forcing hot air down past passengers to reach the floor vents. It also clears out pollutants near the passengers' breathing zones much faster.

The Winter Problem: In the winter, the scenario flips. You're trying to heat the cabin. If you pull all the air out from the top vents, you are just sucking all that nice buoyant warm air straight out of the roof before it reaches the passengers, leaving their feet freezing. It creates massive temperature stratification and makes people incredibly uncomfortable. The study found that in winter, a 50 50 split using both the top and the bottom exhaust provides the best balance. The bottom exhaust pulls the warm air down to feet level, maintaining thermal comfort, while the top exhaust still helps capture the rising respiratory pollutants.

The End of Static Ventilation Design: This proves that static one size fits all vent designs is dead. You cannot have a ventilation system that operates the exact same way in January as it does in July and expect optimal results for both comfort and importantly infection control. We need dynamic systems. If you want to truly manage the risk of airborne transmission in mass transit, while simultaneously hitting our net zero energy efficiency targets, train manufacturers and frankly designers of any large, densely occupied space, need to implement variable exhaust systems that adapt to the season, the thermal load and the occupancy.

The Future of Mass Transit Ventilation: It's a brilliant example of how nuanced, targeted and responsive our ventilation strategies need to become to protect public health in the built environment, especially technical ones like trains. You can imagine the exact same thinking being applied to buses, to aeroplanes and so on. This is the frontier of mass transit air quality management.

https://link.springer.com/article/10.1007/s40534-025-00398-0

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/) - 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)

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.

This week, I step back from the interviews to share a personal reflection on a question that has been nagging at me for some time, sparked by recent encounters with dubious manufacturer claims, the fallout from a prominent Cambridge professor scandal, and my own complicity in wielding peer review as a weapon against innovation: What if the single biggest barrier to progress in air quality and the built environment isn't a lack of good ideas or new technology—but our complete failure to recognise that the gold standard we use to validate truth, peer review itself, is fundamentally broken and built on sand?

Key Topics Discussed:

The Ideal Versus the Reality: In theory, peer review is the guardian of rigorous science. Experts with time and resources deeply interrogate methodology, check references, and provide robust feedback. Papers that genuinely move the field forward are accepted. But the mechanical reality of 2026 is very different. Manuscript submissions have exponentially outpaced the pool of available reviewers. Academics are trapped in a publish or perish hamster wheel. Peer review is unpaid, unrecognised, and unrewarded. Studies suggest just 10% of reviewers handle almost 50% of the global peer review workload. When you have a small pool of incredibly time poor reviewers who are fundamentally overwhelmed, corners get cut.

The Business Model Problem: Over the last decade, there has been a massive shift towards open access and article processing charges. Publishers now make money based on volume, not subscription exclusivity. When authors or institutions pay upwards of two to four thousand pounds to publish a single paper, the publisher is financially incentivised to publish more, not publish better. This environment has given rise to paper mills, highly sophisticated profit driven organisations that manufacture fake or desperately low quality research and sell authorships to desperate academics who need to meet publication quotas.

The AI Closed Loop: Paper mills are using generative AI at industrial scale to produce convincing fake papers that slip past exhausted human reviewers. In response to burnout, an increasing number of time poor scholars are using AI to read papers and write their peer reviews. We are rapidly approaching a closed loop where an AI writes a substandard paper to meet a human's academic quota, submits it to a profit driven journal, and another AI reviews and accepts it on behalf of a burned out human reviewer. The fundamental human element, the actual peer in peer review, is being automated out of existence.

The Consequences for Our Field: In air quality, health and the built environment, bad data passing as peer reviewed science or misleading claims backed up by pseudoscientific marketing has real world consequences. It leads to bad public policy, misallocation of millions of pounds of funding, inadequate ventilation standards, poor building performance and ultimately public harm. We cannot afford a foundation built on sand. We need to rethink the metrics of academic success, recognise peer review as core scholarly labour that needs compensation, and create alternative pathways for validating independent innovation. If we know the traditional peer review monopoly is struggling, we cannot lazily dismiss independent lab data simply because it doesn't carry a specific journal's logo.

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/) - 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)

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.

This week, we dive into a comprehensive review published in the Science of the Total Environment titled Integration of Air Quality Monitoring Systems with Hybrid Electric Vehicles for Emissions Control in Smart Cities, to explore a question that fundamentally challenges how we think about urban air pollution: What if the single biggest opportunity to tackle air quality in our cities isn't just making vehicles cleaner—but transforming them into intelligent, mobile monitoring networks that actively adapt their behavior based on real-time pollution data

Key Topics Discussed:

Adaptive Green Zones: Currently, hybrid cars are incredibly smart internally. They switch between internal combustion engine and battery based on efficiency, charge levels, and acceleration. But they are completely blind to environmental conditions outside the windshield. Imagine integrating a miniaturised air quality monitoring system into the car using IoT sensors and vehicle to everything communication. If a smart vehicle drives into a heavily polluted urban zone, say outside a school at drop off time or a congested city centre, the onboard AI reads the local air quality data and automatically forces the car to switch entirely to battery power. It shuts off the combustion engine. It stops contributing to the local pollution hotspot instantly.

AI Driven Eco Routing: By linking up with smart city infrastructure and using machine learning, these vehicles can use AI driven eco routing. Your GPS wouldn't just find the faster route. It could find a route that minimises your exposure to highly polluted areas, spreading the traffic load and protecting the occupants inside the cabin. It turns the vehicle from a passive polluter into an active dynamic participant in urban air quality management.

The Technical Hurdles: It's not as simple as strapping a sensor to a bumper. We need incredibly robust, low cost sensors that don't lose their calibration every time a car goes over a pothole or experiences a shift in humidity. There's a massive communication challenge. Do we use 5G or DSRC? The latency has to be milliseconds for cars to communicate effectively. And then there's data privacy. Tracking a car's location, speed, and the air it's driven through raises questions. We need standardised, highly secure cryptographic protocols so that data can be shared with city infrastructure without compromising driver privacy.

The Future of Urban Air Quality Management: This is the frontier. The future of clean air isn't just about sticking static expensive reference sensors on a few lampposts around the city. It's about leveraging the millions of vehicles already on the road, turning them into dynamic moving networks of data that physically alter how our cities operate in real time. It's a huge technical challenge, but the payoff for urban health could be transformative.

A comprehensive review on the integration of air quality monitoring systems with hybrid electric vehicles for emission control in smart cities

https://doi.org/10.1016/j.scitotenv.2025.180022

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/) - 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)

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.

This week, we dive into a modelling study published in Environmental Science, Processes and Impacts titled Long-Term Prediction of Climate Change Impacts on Indoor Particulate Pollution, a case study of residential buildings, to explore a question that fundamentally challenges how we think about natural ventilation and climate adaptation: What if the single biggest barrier to maintaining healthy indoor air quality in the coming decades isn't just outdoor pollution—but our complete failure to recognise that rising temperatures are transforming our homes into chemical reactors that generate dangerous ultrafine particles right where we breathe?

Key Topics Discussed:

The Chemistry Problem: Initially, there is some good news. Because of tightening air pollution legislation globally, the baseline outdoor particulate matter, things like PM2.5 and PM10 from traffic and industry, is actually projected to decrease in Europe over the next century. But the chemistry of our indoor spaces is changing. As outdoor temperatures rise, outdoor ozone levels also rise. And as our homes get warmer, the emission rate of volatile organic compounds or VOCs from indoor furnishings increase. When ozone and limonene meet in your living room, they react, and they produce something called secondary organic aerosols, or SOAs, including particulate matter and things like formaldehyde. So while the overall mass of large particles coming in from traffic might drop, the chemistry happening right inside our homes is going to create a whole new soup of ultrafine particles.

Extreme Weather Events: The study didn't just look at average days. It looked at extreme weather events, which we know are becoming more normal. They simulate a Saharan dust storm and an extreme heat wave accompanied by an ozone episode. During the simulated heat wave, they looked at typical human behaviour. We keep the windows closed during the day, and in the evening when it cools down, we throw the windows wide open to purge the heat. But during an ozone episode, when you open those windows in the evening, you are absolutely flooding your home with ozone. The simulation showed indoor ozone levels spiking dramatically, which then reacts with limonene to create massive spikes in secondary organic aerosols.

The End of Natural Ventilation as We Know It: This fundamentally challenges our reliance on natural ventilation in the face of climate change. If opening a window to cool down means inviting in extreme heat, extreme ozone or a massive spike in particulate matter from a dust storm, we simply can't rely on that primary strategy anymore. The paper makes an incredibly compelling case that proper strategies of high efficiency filtration, decent ventilation systems and potentially even scrubbers for gases is going to transition from being a luxury in high end office buildings to perhaps an absolute public health necessity in even our residential homes. Our building envelopes may have to act as an environmental shield against increasingly hostile outdoor atmospheres.

Long-term prediction of climate change impacts on indoor particle pollution– case study of

a residential building in Germany

https://doi.org/10.1039/d4em00663a

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/) - 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)

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.

This week, I step back from the interviews to share a personal reflection on the conversations, themes and patterns that have emerged over the last few weeks, both on this podcast and in the halls and sessions of Indoor Air 2026 in Singapore. What if the single biggest barrier to transforming the built environment isn't our lack of scientific knowledge or technology—but our complete failure to recognise the deeply interconnected systemic, linguistic, economic and human forces that keep us locked in the same destructive cycles?

Key Topics Discussed:

The Linguistic Firewall: During the pandemic, we saw in real time how a single word could paralyse global action. The term airborne became a structural firewall. To an engineer, if a particle is suspended in the air and moves with the air currents, it's airborne. But to the medical community, airborne carries a very specific, high-consequence historical definition. Because of that deeply entrenched medical definition, the engineering and building science communities were effectively locked out of the operational response for months.

The Tyranny of Efficiency: For the better part of the last 40 or 50 years, the dominant almost tyrannical metric in our industry has been efficiency. We chased energy performance relentlessly. Energy is a hard measurable cost. You get a utility bill every 30 days. It is incredibly difficult to put a hard financial number on human health. So we optimize for what we can measure.

The Myth of the Average Person: We design multi million dollar HVAC systems to hold a massive commercial floor plate to a highly precise 21 degrees Celsius. The glaring problem is that the average person is a statistical ghost. When you design for the mathematical average, you are effectively designing for nobody. Instead of viewing human comfort and health as a single fragile optimal point on a graph, we need to view it as a geographical landscape.

The Looming Energy Crisis: The IEA warns of the greatest energy security threat in history. When the grid is constrained, society panics. And when society panics about energy, the built environment is always the first casualty. We know exactly what this looks like because we've been here before. In the wake of the 1973 oil embargo, we sealed our buildings up, slashed ventilation standards and triggered an era of sick building syndrome. The temptation to repeat the mistakes of the 1970s is sitting right in front of us. This is an inflection point. The challenge for all of us is to hold our nerve and fiercely defend the invisible air that sustains us, ensuring that as the world changes around us and as the energy grid strains, we never again compromise the indoor environment.

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/) - 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)

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: Reflections from Indoor Air 2026 and the Power of Conversation
00:01:30 The Crisis Cycle: Why We Design for Emergencies but Operate for Peacetime
00:04:07 The Airborne Language Barrier: When Medical Definitions Paralyze Engineering Action
00:07:11 The Tyranny of Energy Efficiency: How We Optimized Buildings for Spreadsheets Not Humans
00:11:49 The Myth of the Average Person: Why Designing for Statistical Ghosts Fails Everyone
00:16:44 The Comfort Paradox: Is Thermal Perfection Making Us Biologically Fragile?
00:21:46 The Invisibility Problem: Why Data Doesn't Move Hearts and How to Tell Better Stories
00:24:38 Proxies and Noise: The Double-Edged Sword of CO2 Sensors and Simple Solutions
00:27:47 The Accountability Gap: From Run-to-Failure to Mandatory Building Performance Checks
00:32:11 The Global South Crossroads: A Fleeting Window to Leapfrog Western Mistakes
00:35:33 The AI Energy Arms Race: When Data Centers Compete with Humans for Cooling Capacity
00:37:19 The AMR Connection: How Poor Ventilation Fuels the Antimicrobial Resistance Crisis
00:40:10 The Skilled Trades Bottleneck: Why the Workforce Crisis Is Our Greatest Limiting Factor
00:43:09 The 1970s Déjà Vu: Navigating the Energy Crisis Without Sacrificing Human Health Again