[Evaluation and requirements of natural room ventilation]

The current application of the carbon dioxide standard ("Kohlensäuremassstab") of 0.1 vol.-% CO2 given by Pettenkofer 140 years ago is assessed in order to evaluate tolerable indoor air and sufficient indoor air ventilation. For this purpose, criteria by Pettenkofer were contrasted by currently valid criteria. It was found that an actual guidance value should be clearly higher than the one given by Pettenkofer. As confirmed by recent measurements this actual guidance value should be around 0.15 vol.-% CO2. By means of a few examples requirements for indoor aeration of living rooms and classrooms are made evident. The corresponding calculations are based on the indoor air guidance value (i.e. actualised value of Pettenkofer) of 0.15 vol.-% CO2 and are based on respiration rates compiled in "Standards of exposure assessment" by the health authorities of the German federal states. The calculated number of complete renewals of air achieved by circulation shows that recent values given by others concerning the permitted indoor self aeration were set too low and require correction. Applying the demonstrated requirements for indoor ventilation many of the well known problems of indoor air can be minimised or even solved.