1858: Carbon dioxide as an indicator of indoor pollution
The German scientist Max von Pettenkofer started to show interest in the ‘air toxins’ that caused smells in overcrowded rooms. He did not know what sort of poisons they were, how dangerous they might be or how they could be measured but he was satisfied that measuring the levels of carbon monoxide would provide an indirect indication of their presence. He was also aware that carbon dioxide itself was not dangerous in reasonable concentrations. Pettenkofer found that people entering an occupied room would perceive a ‘human smell’ if the concentration of carbon dioxide in the air was more than 1,000 millionths (ppm) above its concentration in the outdoor air. He stipulated this as a suitable maximum level and it is a measure of air purity that still stands today, even if it is sometimes proposed to be changed.
1870s: Ventilation possible using steam engine-driven cooling
The need to cool buildings continued to increase but the creation of cold air was, until then, still achieved by using water sprays, blocks of ice or long underground ducts. Although the first refrigerator had been invented as far back as in 1775 by the Scottish professor William Cullen, it had taken a long time to develop the technology to such an extent that it could provide a feasible solution for buildings. However, in the 1870s, the Swedish locomotive engineer Carl von Linde managed to develop refrigerators for making ice that were considerably more efficient than previous designs. In 1877, one of Linde’s refrigerators was installed in a German brewery, enabling beer to be made in the summertime too. The days of the ice-exporting industry, for example in Norway, were then numbered.
1880s: Ventilation stoves become commonplace, especially in Scandinavia
Tiled stoves had been in use in southern Europe since the Middle Ages but, by the late 1700s, stove technology had been fully refined in Sweden and the same design principles are still implemented today. In the 1880s, the tiled stove was given a special but rather short-lived task – that of driving a hot-air fan. Outdoor air was drawn in at the base of the stove and then released as heated air at the top. The fumes were removed via a chimney, which created an under-pressure that would then suck up the room air. Again, it was heat that was used to drive both the supply air and extract air flows.
1880s: High rooms counteract poor air quality
Primarily for hygiene reasons, the height of rooms had been gradually raised over the years. This made it possible to install high windows with separate, openable frames of which the top part could be used for airing, even in winter. During the 1880s, the heights of rooms reached a maximum and were subsequently reduced.