The aim of the project is to examine whether children's sleep and cognition are affected by exposure to CO2 and other bio effluents during sleep. The participants of the study are 36 children recruited from local schools in Aarhus, Denmark.

The study takes place in the climate chambers at the Department of Public Health, Aarhus University. These chambers allow for experimental testing on humans with advanced exposure generation while avoiding contamination from other sources and controlling temperature, humidity, noise, odor, and light.

The children will be sleeping in the chambers under three different conditions:

• One night of good ventilation with a CO2 level of maximum 800 ppm
• One night of good ventilation with high levels of CO2 (3,000 ppm)
• One night of poor ventilation with high concentrations of CO2 (3000 ppm) and other bio effluents.

The study is a within-group design, and groups of six children will be sleeping in the chambers for three nights (separated by seven days). The different groups of children are exposed to the conditions in a randomized order. The study is double-blinded (of security reasons the persons responsible for CO2 concentrations in the chambers are not blinded).

The study takes place on schools nights. The children arrive at 6 pm and leave for school the morning after. In the evening the children are tested for approximately 30-40 minutes to measure their cognitive performance using CANTAB (Cambridge Neuropsychological Test Automated Battery) on iPads. After completing the test, dinner is served and the children have some spare time before going to bed. During night, the quality of sleep (awake time and different sleep stages) will be monitored using Fitbit devices. Sleep quality will also be evaluated using a short sleep questionnaire. The next morning the cognitive performance of the children will be tested again using CANTAB before the children leave for school.

Our primary hypothesis is that children will perform worse on the cognitive test when exposed to high levels of CO2 and other bio effluents than compared to low levels of CO2 and bio effluents in a well-ventilated room. In addition to that our secondary hypotheses are:

• Children will perform worse on the cognitive test when exposed to high levels of CO2 and other bio effluents than compared to CO2 alone.
• Children will sleep less well in an environment with poor ventilation and high levels of CO2 and other bio effluents compared to sleeping in a well-ventilated room with low levels of CO2.
• Children will sleep less well in an environment with poor ventilation and high levels of CO2 and other bio effluents compared to sleeping in a room with high levels of CO2 alone.
• Children will sleep less well and perform worse on the cognitive test when exposed to high levels of CO2 compared to low levels of CO2.

Inclusion Criteria:

• Healthy children or children with a well-treated chronic disease not interfering with cognition and sleep quality
• Being able to accomplish a CANTAB test
• Completed questionnaires of sleep patterns

Exclusion Criteria:

• Unable to spend three nights (separated by seven days) in the climate chambers
• Conditions that prevent safe access to the chambers such as claustrophobia

The study is double-blinded but a few people in the research team are not blinded because of security reasons (they need to be able to control the concentrations of CO2).