Speed and accuracy are two different scores, and ventilation seems to move one more than the other
Cognitive tests usually give two separate numbers: how quickly you get through the items, and how many of those items you get wrong. In the classroom experiment that varied ventilation between high and low rates, the notable changes appeared across the test measures while the effect on error rates was negligible; only one specific test, the d2 attention test, showed something worth noting on its error-related metrics [1]. In plain terms, the children worked at a different pace, but they did not become noticeably more or less mistake-prone.
That distinction matters for how you read a headline like "better air makes students sharper." A faster processing speed can mean a pupil finishes a worksheet or a timed test in less time, which is a real practical benefit. It is not the same as getting more answers right. The evidence here supports the speed side of that story more clearly than the accuracy side [1].
Why stale air could slow people down without making them sloppier
One plausible explanation is that poor ventilation makes the room feel stuffy and harder to tolerate, and that discomfort eats into the mental effort available for the task. The university study frames ventilation as a major contributor to thermal comfort and indoor air quality, and it found that some classrooms fell short on both comfort conditions and adequate ventilation [2]. If the body is spending effort coping with a warm, stale room, the visible cost may be a slower working pace rather than a burst of wrong answers.
This is an interpretation, not a demonstrated mechanism. Neither study isolates the exact pathway from air quality to processing speed, so the honest reading is that the pattern is consistent with a comfort-and-effort explanation, not proof of it [1][2].
The evidence comes from schoolchildren and university rooms, not from every kind of learner or task
The ventilation-and-lighting experiment was a crossover study in four classrooms, switching pupils between high and low ventilation rates, and it looked at children's performance on cognitive and academic tests [1]. The second study looked at air-conditioned university teaching rooms and relied on self-reported measures of learning performance across various tasks [2]. So the speed-over-accuracy pattern rests on younger pupils in a controlled classroom comparison, while the university evidence speaks more broadly to efficiency and comfort.
Neither study was designed to track error rates or accuracy in detail, which is exactly why the error side of the answer stays soft. The absence of a clear accuracy effect is not the same as proof that accuracy is unaffected; it means these particular measurements did not capture one [1][2].
If you are deciding whether to fix the ventilation, the case is about pace and comfort
For a school or a facilities manager, the practical takeaway is that better ventilation is linked to pupils getting through work more quickly and to rooms that are more comfortable and better ventilated, rather than to a documented drop in mistakes [1][2]. That is still a worthwhile reason to improve air, but it should be described accurately: the measured benefit is about speed and the quality of the indoor environment, not about error-proofing students.
The open question is whether a larger or longer study with careful accuracy scoring would find an error effect that these measurements missed. Until then, the fairest summary is that ventilation mainly appears to change how fast the work gets done [1].
Sources used in this answer
A field study of the individual and combined effect of ventilation rate and lighting conditions on pupils' performance
In a crossover experiment switching four classrooms between high and low ventilation rates, changes appeared across pupils' test performance with a negligible effect on error rates, and only the d2 test showed notable error-related metrics.
Student learning performance and indoor environmental quality (IEQ) in air-conditioned university teaching rooms
In air-conditioned university teaching rooms, ventilation was identified as a major factor in thermal comfort and indoor air quality, with some classrooms failing to meet comfort and ventilation standards, and learning performance was assessed through self-reported task efficiency rather than error rates.