Ventilation rate raises information processing.

What this means

Ventilation rate is how much fresh outdoor air a space brings to each person, usually measured in litres per second per person or read off the CO2 that builds up when air moves too slowly. When a room supplies more fresh air, the people in it work faster and make fewer errors on tasks that need focus: arithmetic, reading, comparing numbers, reasoning through a problem. The effect shows up most in classrooms and offices where people sit for long stretches and CO2 climbs through the day.

What the research shows

Allen (2016) found cognitive scores 101 percent higher on days in a high-ventilation building than in a conventional one, and 61 percent higher in a green building, all at p < 0.0001. Petersen (2016) raised outdoor air from an average of 1.7 to 6.6 litres per second per person and saw correct answers rise across all four tests: addition by 6.3 percent, number comparison by 4.8 percent, grammatical reasoning by 3.2 percent and reading and comprehension by 7.4 percent.

Wargocki (2020) puts the classroom gain at 12 percent in speed when CO2 falls from 2,100 to 900 ppm. Satish (2012) found large drops in seven decision-making scales at 2,500 ppm against 600 ppm, with raw score ratios from 0.06 to 0.56. Zhang (2017) reported slower addition, longer response times and fewer correct links in a cue-utilization test when CO2 from bioeffluents reached 3,000 ppm.

How certain this is

Allen (2016) and Wargocki (2020) support the link, across nine studies spanning field experiments in occupied buildings (Allen 2016), controlled classroom and chamber exposures (Petersen 2016, Zhang 2017, Satish 2012) and a synthesis (Wargocki 2020), and the effect sizes are large and repeatable across arithmetic, reading and decision tasks. The two nulls both sit in one setting: Fan (2023) and Klausen (2023) varied CO2 during sleep and tested the next morning, after people had left the exposure, so they speak to overnight air rather than working during the day. No study reports gains above 10 litres per second per person, so the upper end of the range is untested.

In practice

A room can raise fresh air supply toward 6.6 litres per second per person and expect measurable gains in arithmetic, reading and reasoning tasks, on the scale Petersen (2016) recorded across four separate tests. Where CO2 is already tracked, holding it below roughly 900 ppm rather than letting it climb past 2,100 ppm captures the 12 percent speed gain Wargocki (2020) reports, and this applies to classrooms and offices where people sit through long stretches and CO2 accumulates over the day. Spaces used mainly overnight sit outside this case: Fan (2023) and Klausen (2023) both varied CO2 during sleep and found no next-morning difference in cognitive performance, so a bedroom's ventilation rate should not be treated as a lever on daytime work output unless the occupant is still in that air while working. Above 10 litres per second per person the benefit is unmeasured, so pushing ventilation past that point for cognitive reasons has no supporting figure to aim at. Before crediting a ventilation change with a performance gain, check whether the task and the exposure overlap in time, since the documented effect sits in tasks performed during the fresh air supply, not after people have left it.

Dose and thresholds

Gains run from roughly 2 litres per second per person up to about 10, the range Wargocki (2020) covers; Petersen (2016) measured its improvements moving from 1.7 to 6.6 litres per second per person. Above 10 litres per second per person no data exist, so the ceiling of the benefit is unknown.

Where it is contested

Fan (2023) and Klausen (2023) both found no difference in cognitive performance between CO2 conditions, but each tested the morning after sleep. Fan (2023) exposed people overnight in the bedroom and ran the tests the next day. Klausen (2023) varied CO2 during sleep and tested next-morning after time in well-ventilated rooms, and reported no significant exposure effects on cognitive performance.

Why it happens

Poor air raises arousal and stress: Zhang (2017) found bioeffluents at 3,000 ppm lifted diastolic blood pressure and salivary α-amylase, both markers of a sympathetic response, alongside slower cognitive scores. Fresh air keeps that activation down, so attention holds steady through the day.