In 1858, the German scientist Max von Pettenkofer was interested in the “air toxins“, i.e. smells of the crowded room. He did not know what it was to poisons, how dangerous they were, or how to measure them, but were content to proceed with the measurement of carbon dioxide as an indirect measure of them even though he knew that carbon dioxide itself is harmless in reasonable concentrations. Pettenkofer stated in attempts to visitors coming into the crowded room was met with “human smell” of the carbon dioxide concentration was higher than 1,000 parts per million by volume of air in addition to the outdoor air concentration. He explained why this as an appropriate maximum level, a measure of air purity that virtually stood until today, although it is occasionally advocated other limits.
December 30, 2015