The result: The total amount of bacteria in the discharge air is approx. 90 percent lower than in the intake air. This means that hot air hand dryers reduce airborne bacteria.  This is because hot air hand dryers take the air for drying from their surroundings. If the ambient air contains bacteria, they could end up on clean hands. However, the air is heated sufficiently in the hand dryer to kill any bacteria drawn in with the intake air.
To answer the question, the ipi developed and built the necessary test equipment in cooperation with Institut Fresenius. Several series of tests were carried out. In each case, the bacteria count in the discharge air was below that of the intake air. A statistical analysis on the 95 % level showed that the differentials are significant, i.e. hot air hand dryers reduce the bacteria count in the air. Another series of tests illustrated that the air duct is not a breeding ground for bacteria. No bacteria form in the hot air hand dryer.