###### Abstract  
Conducting physical attendance exams during pandemics is a challenge facing many educational institutes and universities. Our study's main objective is to numerically simulate the expected transmission of the harmful exhaled droplets of aerosols from an infected instructor to students in an exam room ventilated by a number of spiral diffusers. Several critical parameters, including the droplet size, the ventilation rate, and status of the entrance door were considered in the analysis. Two dimensionless indices, i.e., the specific normalized average concentration (\(SNAC\)) and the exceedance in exposure ratio (\(EER\)), were introduced to examine the effect of the said parameters on student exposure to the harmful droplets. The study revealed that the 5 \(\upmu\)m droplets were less hazardous as they resulted in an 87% reduction in exposure when compared with the small 1 \(\upmu\)m size droplets. We also found that when the ventilation rate ratio (\(VRR\)) increased above unity, an upward entrainment process, due to the swirl diffuser, of the aerosol droplets took place, and consequently the risk of student exposure was reduced. The results also demonstrated that increasing \(VRR\) from zero to 1 and then to 2 decreased the exceedance in the student exposure from 3.5 to 2.15 and then to less than zero, respectively. The study also showed that keeping the lecture room's main door open is recommended as this reduced the risk of exposure by 26% in the case of a \(VRR\) equal to 2.  
a 2021 11 9767. [[https://doi.org/10.3390/app11209767](https://doi.org/10.3390/app11209767)]([https://doi.org/10.3390/app11209767](https://doi.org/10.3390/app11209767))  
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Several sources suggested that viruses attacking the respiratory system are transmitted by three routes: (1) large droplets from the infected person that are exhaled with enough momentum to directly impact the mouth, nose, or conjunctiva (eyes) of the recipients; (2) physical contact with infected droplets that are deposited on any surface and subsequently transmitted to the recipient's respiratory mucosa by hand contact; and (3) inhalation by the recipient of infected nuclei (aerosol size droplets) delivered by ambient air currents. The first two routes are referred to as the \"droplet\" or \"contact\" routes of transmission, while the third is called the \"airborne\" transmission route [5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15]. Thus, safety measures should be applied to the airborne route. One of these safety measures for mitigation is to keep sufficient social distance among people. Some researchers estimate that distance to be around 1.5 to 2 m [14]. It is assumed that this distance is feasible and practical, believing that the largest exhaled droplets will eventually settle by gravity or evaporate before moving this distance and affecting the other person. However, several studies have shown that exhaled droplets from breathing, coughing, and sneezing can sometimes travel up to 6 m and even further [16; 17; 18; 19; 20]. Several researchers have studied characterizations of exhaled air velocity, droplet size distributions, and their concentrations during different respiratory activities. However, only a few researchers measured these characters for exhaled air during speaking activities. [PERSON] et al. measured the size of droplets produced during speaking, where they found that the modes of droplet sizes were in the range of 3.5 to 5.5, with corresponding average concentrations in the range of 0.04 and 0.16 particles per cubic cm (cm\({}^{-3}\) or p/cm\({}^{3}\)), respectively. For the entire size range examined of 0.3-20, the average particle concentration produced during speaking was 1.1 cm\({}^{-3}\)[21]. [PERSON] et al. measured an average expiration air velocity of approximately 4.6 m/s for men during speaking, where the geometric mean diameter of droplets was 16.0 and the mode was 6.