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Theory

Time allocation: 10 min.

Indoor air quality​

Important!

Indoors (in a classroom, an office or at home), we often find an unpleasant indoor climate that can lower our performance. The main cause is the amount of CO2 in the air. Because of thermal insulation and window replacement, buildings no longer “breathe naturally”. While the normal CO2 concentration outdoors is 400 ppm (0.04%), indoors it often exceeds 2000 ppm (0.2%). This leads to fatigue, poorer concentration and headaches.

Another important aspect of indoor air quality is thermal comfort, that is, how a person perceives the environment. Objectively, it depends mainly on the air temperature and humidity.

Volatile organic compounds (VOCs) are organic compounds that turn into gas at room temperature. They are the main source of air pollution at ground level. VOC measurements commonly use the quantity “Total VOC”, or TVOC: the combined concentration of several VOCs present in the air at the same time. The acceptable TVOC level is up to 0.5 mg/m³, or 500 ppb (parts per billion), which is 0.00005%. Higher VOC concentrations are considered harmful, because VOCs have a significant effect on human health. They can cause irritation of the eyes, nose and throat, upper respiratory tract infections, nausea, allergic reactions, headaches and other problems. Long-term exposure to higher VOC concentrations can even cause chronic respiratory diseases or lung cancer.

Sources​

  • Biology: the atmosphere (greenhouse gases), photosynthesis, experiments such as measuring the CO2 concentration near plants in an enclosed space (a greenhouse) and comparing the values by day and by night
  • Chemistry: greenhouse gases, dry ice
  • Health education: the effect of carbon dioxide on human health, protecting people (CO2 fire extinguishers)

Examples​