CO2 – the most important indicator of the air quality

airflow, which conducts from outside
Most people spend more than 20 hours in closed rooms every day. The CO2 content (carbon dioxide content) of the air is measured in volume percent, alternatively in ppm (parts per million) and is the most important indicator of the air quality.

A study of the EU Joint Research Centre JCR revealed that the contamination with pollutants is considerably higher in interior rooms than in the outside air. Concentrations, which are harmful to our health in the long run, occur frequently.

• A study according to Pettenkofer proved that people feel comfortable in rooms with a CO2 concentration below 0.1% (1,000 ppm), but feel clearly uncomfortable at levels above 0.2% (2,000 ppm).

• The limit value for living areas in Germany is 0.15% (1,500 ppm) of CO2. In comparison, often concentrations of up to three times as high (up to 5,000 ppm) can be measured in unventilated bedrooms and also in fully occupied classrooms!

To limit the CO2 content to a maximum of 0.15% (1.500 ppm), an average of 25 m³/h of fresh air must be supplied per person, or even more if sport is exercised. Although we actually require only a tenth of this amount for the oxygen supply and for our metabolism, relatively high fresh air flow rates are necessary in order to discharge the CO2-loaded and polluted air. The easiest and most energy efficient way to do this (with heat recovery from the exhaust air), is to implement a ventilation system with heat recovery.

According to DIN standard, the CO2 content should be 30 m³/h multiplied with the number of persons in the building or flat. Against this background, the actual values amount to approximately 20 m³/h in the nursery and 35 m³/h in the bedroom of the parents. The sufficient oxygen supply for our metabolism is of only 10% (!) of the fresh air volume flow, which you need in order to discharge the CO2-loaded and polluted air.

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