## 5 Conclusions  
Our study numerically simulated the transmission of exhaled droplets in a typical 25-seat exam room. The study numerically tracked the ejected droplets from the instructor's mouth while giving 3-min exam guidelines. The model was built using ANSYS-Fluent-Workbench where the RNG k-epsilon turbulence model and the DPM module were chosen for the droplet transmission simulation. The exhaled droplets (of 5, 2.5, or 1 \(\upmu\)m in size) were initially spread out from the instructor's mouth with an initial air velocity of 4.4 m/s. Two key parameters were considered for investigations to study their effects on the students' exposure to the harm droplets: the ventilation rate and the room's door status. Two dimensionless indices were introduced to facilitate the study assessment. The first was a number called the specific normalized average concentration (_SNAC_), which gives a lump-sum estimate for the average students' exposure for the exam room. The second dimensionless number was the exceedance in exposure ratio (_EER_), which provides insight into the spatial variability of the students' exposure to help identify the locations of high-risk spots within the room. The main findings of the study are as follows:  
* The contour mapping of the _EER_ within the exam room, after 180 s, revealed that the students sitting in front of the instructor, especially in the second and third rows, were more susceptible to infection if the ventilation rate does not exceed the minimum recommended ventilation rate by ASHRAE. On the other hand, and as expected, students sitting beside the wall far from the instructor were not affected. * The dispersion of the exhaled droplets inside the room was improved significantly by increasing the ventilation rate. * Increasing the ventilation rate increased the number of affected students. However, it decreased the concentrations to which they were significantly exposed. * Increasing the ventilation rate decreased the specific normalized average concentration (_SNAC_) exponentially. Nevertheless, increasing the ventilation rate ratios above three is expected to have a non-tangible effect on reducing the harmful droplets' exposure. However, more analysis may be required in this regard. Figure 13: The exceedance in exposure ratio (_EER_) after 180 s.  
Keeping the room's main door open at a ventilation rate ratio of 2 reduced the risk of exposure (to the harmful aerosol droplets) by 26%. * Based on the _SNAC_ values for the whole body, the large size (5 \(\upmu\)m) droplets appeared to be less hazardous as they resulted in an 87% reduction in exposure when compared with the small 1 \(\upmu\)m size droplets. * Some students might be subjected to a high risk of exposure (to harmful droplets) that exceeded 3.5 times the average reference risk in the case of no ventilation. In this paper, the normal speaking process of the polluting instructor was modeled. However, coughing or sneezing processes with high initial velocities may result in different transmission behavior of exhaled droplets. Having a student as a polluting source may need to be further studied when sitting at various locations. These points and other scenarios are essential to further investigate to enhance our understanding of droplet transmission in education facilities. Conceptualization, M.I.F. and A.F.N. ; methodology, M.H.E. and M.I.F. ; software, M.H.E. and M.I.F. ; validation, M.I.F., A.F.N. and M.H.E. ; formal analysis, M.H.E. and A.F.N. ; investigation, A.F.N. and M.H.E. ; resources, A.F.N. ; data curation, M.H.E. ; writing--original draft preparation, M.H.E. and A.F.N. ; writing--review and editing, M.H.E., M.I.F. and A.F.N. ; visualization, M.H.E. and A.F.N. ; supervision, M.I.F. ; project administration, M.I.F. ; funding acquisition, N/A. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Data Availability Statement: Data are available on request from the authors.