https://medicalxpress.com/news/2023-05-reveals-poor-bedroom-air-quality.html

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If ventilation keeps CO2 from persons sleeping in a bedroom below 750 ppm, then the air quality in the room is so good that it does not affect sleep quality. If CO2 exceeds 2,600 ppm, the air quality is so poor that it affects sleep quality to such an extent that cognitive abilities are affected the next day; this may also be the case at lower CO2 concentrations.

CO2 is used as an indicator of how good the ventilation is in rooms where there are people. Indoor CO2 is mainly released by humans due to the metabolic processes of the body. The concentration is measured in mg/m3 or in ppm (ppm, parts per million, refers to the number of carbon dioxide molecules per million molecules of dry air).

Below 750 ppm: Adequate ventilation—no negative effect on sleep quality. This will be a typical measurement for a well-ventilated bedroom.

Between 750 ppm and 1150 ppm: Possibly insufficient ventilation—in some cases, sleep quality may be adversely affected.

Above 1150 ppm: Insufficient ventilation—sleep quality will be adversely affected. CO2 levels that are higher than 1150 ppm will typically occur in bedrooms that are not fitted with a ventilation system and where windows and doors are closed.

Above 2600 ppm: Insufficient ventilation—both sleep quality and next-day performance are adversely affected.

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