The air inside most meeting rooms is fundamentally different from the air outside.

The moment people enter, the space begins to change.

Every person exhales carbon dioxide.

If the room has poor ventilation, carbon dioxide accumulates faster than it can escape.

This is not just a comfort issue. It is a cognitive one.

Controlled studies consistently show that as indoor carbon dioxide levels rise, the brain becomes slower, less accurate and more fatigued. Research demonstrates measurable declines in decision-making, working memory and reaction speed at concentrations commonly found in busy offices and enclosed meeting spaces [1,2].

In meeting rooms with no access to fresh outdoor air, carbon dioxide can move from baseline to performance-impairing levels in less than fifteen minutes [1,3]. This is the point at which people experience the very symptoms we misinterpret as disengagement: fogginess, tiredness, irritability and reduced clarity.

A Necessary Clarification: CO₂ Does Not Reduce Oxygen Uptake

This is important.

Carbon dioxide at levels typically found indoors does not reduce oxygen levels in the air.
Oxygen remains approximately twenty-one per cent.
There is no pulmonary hypoxia.
There is no impairment in oxygen diffusion.

The cognitive decline is not caused by low oxygen.

It is caused by how the brain responds to rising carbon dioxide.

Even moderate increases activate chemoreceptors in the brainstem that regulate breathing and arousal. This subtle shift alters autonomic balance, introduces neural noise and increases the biological effort required to think clearly. In simple terms, your brain has to work harder to perform the same task.

These effects happen long before oxygen ever becomes a limiting factor [1,4].

Ventilation: The Difference Between Thinking and Surviving a Meeting

Most meeting rooms rely on:

• Air Conditioning Units

• Fan Coil Systems

• Split Systems

• Recirculation-Based Hvac

These systems cool or move air but they do not replace it.

Without mechanical fresh-air intake, the carbon dioxide people exhale remains trapped in the room.

Opening a door does not resolve the problem.

A desk fan does not resolve the problem.

A purifier does not resolve the problem.

Only ventilation that brings in new outdoor air and removes stale indoor air can keep cognitive performance stable.

According to measurement studies, many meeting rooms fail to deliver anywhere near the recommended levels of fresh air for healthy cognitive function [5]. And when ventilation is inadequate, performance declines are unavoidable.

It is Never Just One Variable: The Big Seven of Human Performance Indoors

Carbon dioxide is the most visible indicator of poor ventilation, but it is not the only factor.

The brain responds to the combined load of what we call the Big Seven environmental determinants of performance:

1. Carbon Dioxide
2. Temperature
3. Humidity
4. Light Quality
5. Particulate Matter
6. Volatile Organic Compounds
7. Noise

When these factors drift outside optimal ranges inside a sealed room, cognitive performance begins to deteriorate.

Temperature that is slightly too warm.

Humidity that is slightly too high.

Lighting that suppresses alertness.

Particulate pollution or VOCs that create inflammatory load.

Noise that disrupts processing.

Individually these stresses may seem small. Together they materially change how the human brain performs [2,5,6].

This is one of the primary drivers behind what is known as Sick Building Syndrome: environments that quietly erode mental clarity, energy, resilience and wellbeing across the working day [7].

A Case Study: What Actually Happens Inside A Typical Meeting Room

To make this real, let us look at a standard meeting room profile and what happens to the biology of the space over time.

Room profile

• Size: 5 m x 5 m

• Ceiling height: 2.8 m

• Volume: roughly 70 cubic metres

• Location: typical city office, sealed facade

• Ventilation: air conditioning only, no dedicated fresh air supply

• Occupancy: 12 people seated, talking

• Starting outdoor CO₂: approximately 450 parts per million

Each person in the room is quietly generating CO₂ as they breathe. A typical seated adult who is talking produces around 0.3 litres of CO₂ per minute. With 12 people in the room, that is:

• 0.3 litres per minute x 12

• 3.6 litres of CO₂ per minute

• 216 litres of CO₂ per hour, or 0.216 cubic metres per hour

In a 70 cubic metre room with no meaningful fresh air, that CO₂ has nowhere to go.

If we look at the change in concentration over time, the maths is simple:

• CO₂ added per hour: 0.216 cubic metres

• Room volume: 70 cubic metres

• Increase per hour: 0.216 / 70 ≈ 0.0031 as a fraction of room air

Convert that to parts per million and you get a rise of around 3100 ppm per hour.

Starting at 450 ppm, the room now looks like this.

• 0 minutes: 450 ppm, people walk in, everyone feels fine

• 15 minutes: approximately 1200 ppm

• 30 minutes: approximately 1950 ppm

• 60 minutes: over 3000 ppm

These are not exotic numbers. They are what you see every day when you put a CO₂ monitor in a sealed meeting room.

Even if the building has small leaks or very light ventilation that halves the effective build up rate, you are still above 1000 ppm within the first 15 to 20 minutes of the meeting. That is exactly the range where controlled studies begin to show measurable drops in decision making, response speed and higher order thinking [1,3,4].

From a human point of view, this is what people experience.

• First 10 minutes: normal engagement, novelty effect, everyone feels present

• Around 15 minutes: the first signs of heaviness, people shift in their seats, focus begins to drift

• 20 to 30 minutes: more yawning, more mental effort required to stay with the discussion, a sense of “brain fog”

• Beyond 30 minutes: people struggle to hold complex ideas, the room feels stuffy, decisions become slower and more conservative

Nothing about the content of the meeting changed.

The biology of the room did.

This is why you can run the same agenda in two different rooms and get a completely different level of energy, clarity and output. One space is working with the human brain. The other is working against it.

For organisations, the implication is clear. A “standard” internal meeting room that looks perfectly functional on paper can shift into a cognitive impairment environment inside the first quarter of an hour, long before most people realise what is happening.

If you want better thinking, you have to start by changing the conditions people think in.

Why This Matters More Than Ever

Work today demands higher cognitive output than at any point in history.

People are required to think fast, communicate clearly, collaborate effectively and make high-quality decisions under pressure.

Yet many of the spaces designed for those very activities compromise the biology required to perform them.

This is not a design flaw. It is a knowledge gap.

We have prioritised acoustics, furniture and finishes over ventilation quality.
We have built sealed, energy-efficient rooms that inadvertently degrade human cognition.
We have invested in technology and collaboration software, while ignoring the physical determinant of human thinking: the air people breathe.

If organisations want clearer conversations, better ideas and more productive meetings, they must begin with the biology.

Human performance does not start with motivation.

It starts with environment.

A Better Way Forward

Improving meeting room performance does not require a complete redesign. It starts with understanding your environment.

Measure carbon dioxide.

Measure temperature, humidity, light and particulate load.

Look at whether fresh air is entering the space.

Assess how quickly the room recovers between meetings.

Understand how many people the room can realistically support.

Once you see the data, the path to improvement becomes obvious.

Better ventilation.
Better air exchange.
Better environmental control.
Better performance.

These are not wellness upgrades.

They are productivity investments.

If you want your meeting rooms to support the way people think

Feel free to reach out.

We assess environments across the Big Seven and help organisations create spaces that protect clarity, energy and high-quality decision-making.

When you design for biology, performance follows.

References

1. Allen, J. G., MacNaughton, P., Satish, U., Santanam, S., Vallarino, J., and Spengler, J. D. (2016). Associations of cognitive function scores with carbon dioxide, ventilation, and volatile organic compound exposures in office workers. Environmental Health Perspectives, 124(6), 805 to 812. https://doi.org/10.1289/ehp.1510037

2. Yun, S., and Licina, D. (2023). Investigation of personal air pollution exposures and occupants’ fresh air demands in office buildings in Switzerland. Journal of Physics Conference Series, 2600, 102010. https://doi.org/10.1088/1742-6596/2600/10/102010

3. Chen, D., Bagkeris, E., Mumovic, D., Huebner, G., and Ucci, M. (2023). Effects of elevated carbon dioxide levels on response speed in cognitive tests. E3S Web of Conferences, 396, 01040. https://doi.org/10.1051/e3sconf/202339601040

4. Turanjanin, V., Vučićević, B., Jovanović, M., Mirkov, N., and Lazović, I. (2014). Indoor carbon dioxide measurements in Serbian schools and ventilation rate calculation. Energy, 77, 290 to 296. https://doi.org/10.1016/j.energy.2014.10.028

5. Eichholtz, P., Kok, N., and Sun, X. (2023). The effect of post COVID 19 ventilation measures on indoor air quality in primary schools. PNAS Nexus, 3(1). https://doi.org/10.1093/pnasnexus/pgad429

6. Wu, R. (2025). Distributed direct air capture by carbon nanofiber air filters. Science Advances, 11(42). https://doi.org/10.1126/sciadv.adv6846

7. Arikan, I., Tekin, O., and Erbas, O. (2018). Relationship between Sick Building Syndrome and indoor air quality among hospital staff. La Medicina del Lavoro, 109(6), 435 to 443. https://doi.org/10.23749/mdl.v110i6.7628