Amayu Wakoya Gena (MSc) and Professor Conrad Völker from the Professorship for Building Physics were already using the Schlieren mirror in March to show how the air we breathe is spread when we cough with and without covering our mouth and nose. The visualisation attracted a great deal of media interest, particularly in light of the social distancing measures and obligation to wear a face mask due to the coronavirus pandemic. The experiment in the Schlieren laboratory has now been repeated to test the effectiveness of the newly developed »BauhausUniVisor«.

Professor Andreas Mühlenberend – who developed the visor together with Assistant Professor Jason Reizner and Kristian Gohlke – was himself the test subject, standing before the test set-up with a Schlieren mirror and high-resolution camera for the experiment. Different scenarios were tested, namely breathing, coughing and speaking. The air breathed was visualised without his mouth and nose being covered, then again while wearing the visor. The outcome: no exhalation clouds are visible outside the visor directly in front of the wearer, as the air breathed is diverted downwards and upwards by the protective film in front of their face. In contrast, without the protective visor, the air breathed spreads at different speeds and far out in front of them.

It is important to note that the turbulence below Professor Mühlenberend’s head and the air rising above it due to body heat (natural convection) occurs independently of the air we breathe and is also visible in front of the Schlieren mirror. The Schlieren mirror test does not provide any information on distribution of the liquid particles known as aerosols suspended in the air.

Despite the visor’s effect, which can be seen in the video, the experiment’s participants emphasise that it is still important to adhere to social distancing and all instructions issued by the health authorities and particularly to maintain an appropriate distance if you are experiencing symptoms.