Instrument for measuring carbon dioxide in room air, maker: Drägerwerk/Lübeck, 1943, approx. 14.0 (diameter) × 15.0 cm (excluding the container), metals, glass, paper, etc. KIT Archives 28509/4.
This CO₂ measuring device dates back to 1943 and was discovered in a basement room at KIT, which presumably had served as an air-raid shelter during World War II. In a crowded air-raid shelter, measuring the CO₂ content of the air was potentially vital, as the oxygen could quickly become depleted when many people were staying there. The instruction manual reveals that operating the device was complex and prone to error. Even just initially setting it up involved six steps, and the part on “conducting a room air test” added five more. Proper use of the device surely required practice, especially during an emergency. After fanning the room air into the device, it had to be sealed tightly. Inside, tissue-paper disks drenched in alkaline lye absorbed the CO₂. This created a negative pressure that was displayed on an oilscale connected to the measuring chamber. The higher the value on the oil scale, the poorer the air quality. Measurements had to be taken regularly, as the device only displayed the momentary air quality.
Most of the buildings of Karlsruhe Polytechnic were heavily damaged during the air raids. Mechanical Engineering Professor Rudolf Plank (1886–1973) noted in his memoirs about the year 1944: “The tragic end of the ‘thousand-year Reich’ became apparent to all those with insight, but the Party was still making a big show of itself. The bombing raids on German cities multiplied, and the civilian population was fully engaged in the war. University teaching and academic work almost completely ceased, and the bunkers had to be visited more and more frequently.” as