## 4 Discussion  
If studies are conducted indoors, the room-specific conditions must be observed. The concept shows how to reduce the risk of infection, but it must be adapted to the available space. In particular, ventilation conditions are crucial as infection can occur despite social distancing indoors [5]. Fans and suction systems that move air laterally should not be used, as this can actually increase the risk of infection via aerosols and droplet cores [22]. The amount of time an individual is in the room should be kept at a minimum [4]. This is of particular importance in smaller rooms. If the available space is dissimilar from the concept, the risk of infection in the study-specific case can be reduced through the division of the testing areas. Markings help maintain a 1.5 m distance between individuals. This is only relevant, however if the paths between stations cross and the room planning in Figure 4 is impossible. During the study, occupancy of the test site should be kept to a minimum to further reduce the infection risk. Studies conducted in vehicles are a more challenging case as they offer a smaller space where a diagonal seating arrangement must be employed for a maximum of two individuals to be spaced safely more than 1.5 m apart. The use of a partition further reduces the risk of infection. In most cases, the dividers are not airtight and therefore, only prevent droplet infections and not aerogenic infections because the air and virus-containing particles can flow around the protective walls [3]. Partitions do significantly slow down the distribution of aerosols and droplet cores in the vehicle [9]. The air exchange rates similarly play an important role in smaller spaces such as a vehicle. Opening the car windows as the weather allows should complement the operation of the ventilation as an infection protection measure. The use of the air circulation on the other hand is not recommended, since it would block out fresh air and aerosols and droplet cores are not removed leaving occupants at heightened risk of infection [30]. When selecting subjects, those who are vulnerable and part of at-risk groups should be avoided. If absolutely necessary, these individuals can participate provided their risk of infection can be reduced through comprehensive testing including a rapid test at the study start. It should be noted that a less representative statistical distribution of the total population risks the quality of the study outcome even when populations are excluded for reasons of safety. Figure 10: Disinfection of the experimental environment. Studies occurring during a pandemic, require unnecessary encounters to be avoided. Arrival times for subjects, for instance should be staggered and reception and pre-examination areas must be prepared. The participating subjects must be informed about hygienic measures. Throughout the study, adherence to the respiratory mask, social distancing and hygiene mandates are required. Preliminary examinations shall test subjects for symptoms, the virus or even potentially antibodies in order to prevent infected people from participating. Since rapid tests in particular are only a snapshot and can be less accurate than PCR tests, caution is required. That's why a positive rapid test needs to be confirmed by a PCR laboratory test [31]. The offsetting of participant arrivals also creates clarity made possible by good organization. These positive characteristics are also worthwhile for studies not occurring in the midst of a pandemic. After each trial, disinfection is required to protect the next subject from a possible infection. Disinfecting wipes are used to prevent indirect contact infections, and ventilation prevents aerogenic infections. When disinfecting, gloves and respiratory masks must be worn. The use of trained cleaning personnel for this task should be discussed. This should not be mandatory, as the disinfection process is relatively easy and straight forward. Furthermore, there are different types of disinfection.