The effects of bedroom air quality on sleep and next-day performance

This examination come from Technical University of Denmark using their facilities.

https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12254

A subjects were divided to 2 groups and put them to identical room.

First examination was for 14 subjects, it is designed average CO2 level was 2585 or 660ppm difference.
On the other hand, 16 subjects were in controlled room, which used an inaudible fan in the air intake vent for making average CO2 level was 2395 or 835pmm. It should have exceeded 900ppm.

How to assess sleep quality was a wrist watch called actigraphs to measure their movement data, and subjects recorded their perceptions and their well-being each morning using online questionnaires.

They were tested their mental performance by two questions below.
1. Objectively, checking their sleep quality.
2. How they felt integrity on bed room air subjectively.

The result was when the lower CO2 was, the more improved sleepiness and concentration and performance for logical thinking test effectively.