Clean air means brain power

October 21, 2021 – 2 Min

Poor indoor air quality doesn’t just make us unhealthy. A new study from Harvard University shows that it makes us less productive too.

Direct correlation

The study tracked office workers (with an average age of 33) in commercial buildings in six countries – China, India, Mexico, Thailand, the USA and the UK – over a 12 month period. 

It points to a direct relationship between the amount of fine particulate matter in the air and how people perform in mental tests. The more polluted the air, the worse people perform.


The study used monitors to measure ventilation and indoor air quality in the buildings,

including levels of fine particulate matter, known as PM2.5. This is made up from dust, bacterial spores, allergens, smoke, outdoor air pollution, etc.

The workers were asked to use an app to take regular cognitive tests during the workday.

These tests included Stroop colour-word tests and addition-subtraction (ADD) tests to measure working memory and attention.


The study found that higher PM2.5 and lower ventilation rates, the latter assessed by CO2 concentration, were associated with slower response times and reduced accuracy (fewer correct responses per minute) on the Stroop and ADD for eight out ten test metrics.

Each interquartile increase in fine particulate matter of just 8.8 micrograms per cubic metre was associated with a 0.82% increase in Stroop response time, a 6.18% increase in Stroop interference time, a 0.7% decrease in Stroop throughput, and a 1.51% decrease in ADD throughput. 

Those percentages quickly escalate as the concentration of particulate matter builds up in a shared office environment. 


The findings support an earlier study on the impact of green buildings by the Harvard Center for Health and the Global Environment. It showed that, with better air quality, cognitive scores were 61% higher across nine functional domains, including crisis response, strategy, and focused activity level.

Clean air improves brain power, which in turn boosts retention, output, innovation and strategic decision making. 

Any investment in clean air is not just about protecting health and preventing sick building syndrome, but about activating a higher performing workforce.

Poor air quality remedy  

Poor indoor air quality is an easily solvable problem. 

The WHO’s updated ventilation recommendations stipulate ventilation rates of: 160 litres per second per patient within healthcare settings; and 10 litres per second per person within non-residential indoor environments. If the HVAC system in a building is unable to achieve  the optimum air change rate, the gap must be bridged.

That can easily be done using portable air purification using HEPA filtration to trap fine particulate matter and  germicidal UVC light to destroy it, as recommended by authorities including the WHO, CDC, SAGE, EPA, CIBSE and the HSE.

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