How Air Quality Impacts Productivity, Cognition, and Performance

How air quality affects productivity

Productivity is usually discussed in terms of people, processes, and skills. Rarely does the conversation start with the air itself. Yet a growing body of research shows that what employees breathe each day has a measurable, quantifiable influence on how quickly they think, how accurately they work, and how well they perform.

Indoor air quality and wider indoor environmental quality are no longer just comfort or wellbeing topics — they're performance variables, and researchers now have the figures to prove it. Below, we've pulled together the key studies behind this shift, what each one actually found, and what it means for buildings still running on "if nobody's complained, it must be fine."

How does CO2 affect productivity?

Carbon dioxide is not harmful at typical office levels, but it's an excellent indicator of how well a space is ventilated. When CO2 rises, it usually means fresh air is limited, and the cognitive effects begin to appear, often well before anyone notices the room feels "stuffy."

In a year-long multinational study of more than 300 office workers, higher indoor CO2 levels were linked to slower response times and reduced mental throughput, even though concentrations remained within ranges widely accepted for offices. Participants took longer to complete attention and arithmetic tasks and produced fewer correct answers per minute.

In practice, according to these findings, inadequate ventilation affects your cognitive abilities long before anyone complains about stale air. If you think poor air quality is impacting the productivity in your workplace, check out our air quality monitoring and ventilation validation services for support.

If you're particularly concerned about high carbon dioxide in the office, we've got a blog just on that topic. If you're looking for a sensor, check out our workplace IAQ sensor guide.

Fine particulates might affect accuracy and reaction speeds: The evidence

Ventilation is only part of the picture. Fine particulate matter (PM2.5) plays an equally important role. The same Harvard study found that as PM2.5 levels increased, workers showed slower reaction times and lower accuracy, particularly once concentrations rose above 12 µg/m³ — a level commonly found in urban indoor environments, including many UK city-centre offices.

Experimental research reinforces this: task performance falls by around 1% for every 10 µg/m³ increase in PM2.5. A separate industrial-safety analysis goes further, associating a 10 µg/m³ rise in PM2.5 with a 26.3% increase in cognitive error probability during complex tasks — a figure with obvious implications for sectors like engineering, healthcare, and finance, where a single mistake carries real cost. These aren't dramatic collapses in performance, but subtle, compounding degradations that eat away at a worker's ability to think and work efficiently over the course of a day.

Not all air quality studies agree

Most of the evidence above comes from observational or single-pollutant experiments, and a smaller but growing set of tightly controlled trials has struggled to reproduce the size, or direction, of these effects.

The most rigorous challenge so far comes from a 2026 randomised controlled trial by Herbig, Mayer, Norrefeldt and Wargocki, published in the International Journal of Hygiene and Environmental Health. The researchers exposed 398 healthy adults to eleven combinations of CO2 (1,200–4,200 ppm), atmospheric pressure, and a VOC mixture (up to 2,100 µg/m³ TVOC), then tested eight distinct cognitive domains. They found effects in only two of the eight domains tested, and critically none of the differences lined up systematically with air quality conditions. Their conclusion was that short-term exposure to these pollutant levels showed no systematic negative effect on cognitive performance in healthy adults, though they noted their TVOC mixture may not represent every real-world blend, and called for longer-exposure studies to settle the question.

This sits in direct tension with the green-building study from Harvard's T.H. Chan School of Public Health, often cited as the strongest evidence in the other direction. Allen et al. (2016) placed 24 participants in simulated "Conventional" and "Green" office conditions over six full work days, varying VOCs, ventilation rate, and CO2 independently. Cognitive scores were 61% higher on Green building days and 101% higher under Green+ (high-ventilation) conditions than on Conventional days, with effects across all nine domains tested.

Both studies used controlled, blinded exposure designs and established cognitive test batteries — yet reached largely opposite conclusions, which says as much about the difficulty of isolating IAQ's cognitive effect as it does about either individual study.

One possible explanation is that people themselves are unreliable narrators of air quality. A separate study from the same German research group behind the 2026 trial found that participants' self-reported environmental sensitivity, not the actual pollutant exposure, was the stronger predictor of how they rated air quality and wellbeing; individuals who saw themselves as more sensitive rated air quality worse regardless of the real exposure condition. The authors concluded environmental sensitivity should be treated as a confounding factor in exposure studies, which may partly explain why perception-based and outcome-based studies in this field don't always agree.

Air quality still affects how people feel at work

Even where cognitive test scores hold steady, indoor air quality still shows a consistent, independent relationship with self-reported symptoms and mood. A study of 417 office employees across eight high-rise buildings in Taipei found that for every 100 ppm rise in the gap between indoor and outdoor CO2, the odds of reported tiredness rose by 16% and dizziness by 22%. TVOCs were independently linked to irritability and difficulty concentrating. None of this required a controlled lab setting to show up — it was measured directly in working offices using portable monitors over full shifts.

In other words, whether or not poor IAQ measurably dents test scores in a given study, it correlates fairly consistently with workers feeling worse, and feeling worse at work is its own cost, in absenteeism, morale, and staff retention, independent of any cognition debate.

The evidence, study by study

It's worth being specific about where these figures come from, since "studies show" is doing a lot of unearned work in most air quality content online. Here's a breakdown of the key studies referenced throughout this article:

1. Harvard T.H. Chan School of Public Health (2021) — The 300-worker, six-country study referenced above. Each participant's workspace was fitted with a sensor tracking real-time PM2.5 and CO2, and cognitive performance was tested using the Stroop colour-word test (attention control and inhibition) and timed arithmetic tasks (processing speed and working memory), rather than self-reported fatigue surveys. This is one of the largest and most methodologically rigorous studies in the field, and the one most other IAQ-productivity content ultimately traces back to.

2. D.P. Wyon, "The effects of indoor air quality on performance and productivity" (2004) — A widely cited review of controlled office-work experiments, some running up to five hours, that varied outdoor air supply rates from 3 to 30 litres per second per person. It concluded that poor indoor air quality decreases productivity "beyond reasonable doubt," with measured effects on office work performance of 6–9% — a figure now used across the industry as a baseline for cost-benefit modelling on ventilation upgrades.
   

3. R. Gupta et al., "Defining the link between indoor environment and workplace productivity in a modern UK office building" (2019) — An office-based study in southern England conducted with the help of facilities management company Emcor which compared the indoor CO2 concentrations against the workers' cognitive task scores. The study found a 15% decrease in scores when CO2 levels were above 800ppm. The study found carbon dioxide to impact reaction times, decision making ability, and increased tiredness. The researchers also point out that our reliance on mechanical ventilation has meant that modern buildings come 'sealed', so natural ventilation from windows is reduced to a minimum.

4. MIT Department of Urban Studies and Planning, "Human health and productivity outcomes of office workers associated with indoor air quality: a systematic review" (2021) — A macro analysis of existing research papers on air quality and its effects on health and cognition; 42 separate studies were reviewed, concluding that workers exposed to conditions above ASHRAE's minimum ventilation standard (17 CFM per person, CO2 steady-state below 1,000 ppm) consistently showed poorer health, performance, and productivity outcomes across a broad range of industries and roles — reinforcing that this isn't an office-specific quirk, but a consistent pattern across building types.

5. Lu et al., "Building-Related Symptoms among Office Employees Associated with Indoor Carbon Dioxide and Total Volatile Organic Compounds" (2015) — A field study of 417 Taipei office workers linking CO2 and TVOC exposure to tiredness, dizziness, irritability, and difficulty concentrating, independent of any formal cognitive testing.

6. Herbig et al., "Do carbon dioxide, volatile organic compounds and atmospheric pressure affect the cognitive performance of occupants in indoor environments?" (2026) — A large randomised controlled trial (n=398) that found no systematic cognitive effects from CO2 up to 4,200 ppm or TVOCs up to 2,100 µg/m³, directly challenging the smaller cross-over studies this field has historically relied on.

7. Allen et al., "Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers" (2016) — A blinded, controlled six-day exposure study comparing simulated Conventional and Green office conditions. Found cognitive scores 61–101% higher under improved ventilation and lower-VOC conditions, across all nine domains tested.

How is productivity actually measured?

What makes the strongest studies in this field compelling — on both sides of the debate — is how performance was tested. The better-designed research doesn't rely on perception surveys alone; it uses established cognitive tools such as the Stroop colour-word test and timed arithmetic tasks, which measure attention control, processing speed, inhibition, and working memory. This is also why the 2026 Herbig trial carries weight even though its findings cut against the industry's usual narrative: it used the same rigour, at a larger scale, and simply found a different result.

Does better ventilation help you work faster?

When ventilation improves, performance improves with it. A meta-analysis pooling five studies and 47 experiments, covering 3,679 participants in total, found that higher ventilation rates consistently produced faster task completion and lower error rates. Arithmetic task speed improved by 13.7% and broader cognitive ability by 3.5%, while arithmetic error rates fell by around 16.1% in better-ventilated conditions. The strongest effects appeared in poorly ventilated spaces, suggesting many buildings are still operating well below their cognitive optimum — and that the fix, in many cases, is a ventilation and filtration review rather than a wholesale refit. 

Does poor air quality cause workers to make more mistakes?

Productivity is often equated with output volume, but in most workplaces, quality matters just as much. Poor air quality has been shown in some studies to slow responses and increase the likelihood of mistakes. For roles involving design, finance, healthcare, or engineering, small increases in error probability can outweigh any gains in pace — increasing rework, review cycles, and operational risk. A 26% jump in error probability, as found in the PM2.5 research above, is more than just an occasional slip-up, it's a real and recurring cost to any business. 

Is air quality important for workplace productivity?

Ventilation rates, filtration efficiency, particulate control, and thermal stability are not merely comfort settings. They're performance levers. Buildings that control CO2 and PM2.5 effectively create conditions where people can be more comfortable, think faster, make fewer mistakes, and sustain concentration for longer. Across an entire workforce, even modest cognitive gains (5% - 10% are clearly attainable) can translate into significant business value over a year.

Multiple independent studies — including blinded exposure trials and large field studies — continue to find real associations between IAQ, cognitive scores, and self-reported wellbeing. 

On the other hand, there has been a real shift in IAQ studies in recent years which conflicts with the classic idea that poor air quality equals poor cognitive performance. It just might not be that simple.

The honest summary of the evidence is this: the largest and most rigorous single RCT to date found no systematic cognitive effect from CO2 or VOCs at the levels tested, and that finding deserves to be taken seriously and weighted fairly against contrasting studies in IAQ discussions. The field hasn't settled the question of exactly how much IAQ affects raw cognitive output, but the evidence for its effect on comfort, symptoms, and mood is considerably more consistent.

Healthy air, healthy staff, a workplace people actually want to be in. That's still worth investing in.

Reach out to us

We offer a range of services which help to increase ventilation rates, reduce pollutant levels, and increase wellbeing and productivity. Get in touch with one of our experts if you have any questions on whether your workplace could benefit from ARM Environments' professional IAQ or HVAC services.