# Bacteria Filtration Efficiency for Different Types of Protective Face Masks
## 3 Results and Discussion
Analyzing the projections of the case distributions on the factor plane, it is evident that most of the observations or analyzed cases are distributed on the right side of main component p1, which leads to the assumption that surgical and FFP2 masks applied at all locations (A, B, C, and D) define the right side of component p1. The left side of principal component p1 is defined by the single-layer cloth mask at all locations. Furthermore, the first quadrant shows the distribution of cases that have the strongest impact on the applied model, including the efficiency of air filtration, namely the application of FFP2 masks at all locations and surgical masks at locations A and C. The applied surgical mask at location B also had a significant impact on the applied model but was weaker because it is distributed in the second quadrant. The surgical mask at location D and the single-layer cloth masks applied at all locations were weak or ineffective in filtering bacteria. Meanwhile, the comparison of the variables and case distribution presented in Figure 5a,b indicate that FFP2 and surgical masks (except at location D) proved to be effective in filtering all analyzed bacteria. It should be noted that yeasts and _Bacillus_ spp. were completely filtered by the applied FFP2 and surgical masks. Furthermore, by using FFP2 and surgical masks, good filtration of the following bacterial species was achieved: _S. aureus_, _M. luteus_, and _A. lwoffi_. Finally, it can also be observed that single-layer cloth masks have a very poor ability to filter the analyzed bacteria and should be replaced by either surgical or FFP2 masks. Figure 6 shows a three-dimensional (3D) surface plot showing the effectiveness of bacterial filtration (_Bacillus_ spp., _A. lwoffi_, and _S. aureus_) with single-layer cloth, surgical, and FFP2 masks from locations A, B, C, and D obtained using PCA. The 3D surface and contour plots represent a response surface with a simple maximum. The plot shows the responses between the analyzed bacteria with different colors, from lighter to darker, together with the numerical response values (from \(<\)-460 to \(>\)100). As the color becomes darker, the response increases. It can be concluded that there \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multirow{2}{*}{**Variable**} & \multicolumn{4}{c}{**Eigenvectors Spreadsheet**} & \multicolumn{4}{c}{**Variable Contributions**} \\ \cline{2-7}  & **p1** & **p2** & **p3** & **p1** & **p2** & **p3** \\ \hline Yeasts & 0.37 & \(-\)0.01 & 0.11 & 0.14 & \(<\)0.01 & 0.01 \\ _Acinetobacter lwoffi_ & 0.37 & \(-\)0.17 & 0.05 & 0.14 & 0.03 & \(<\)0.01 \\ _Bacillus_ spp. & 0.36 & \(-\)0.01 & \(-\)0.24 & 0.13 & \(<\)0.01 & 0.06 \\ _Corynebacterium_ spp. & 0.27 & 0.37 & 0.28 & 0.08 & 0.13 & 0.08 \\ _Microoccus luteus_ & 0.37 & \(-\)0.16 & \(-\)0.07 & 0.14 & 0.02 & 0.01 \\ _Microococcus_ spp. & 0.26 & 0.45 & 0.20 & 0.07 & 0.20 & 0.04 \\ _Staphylococcus aureus_ & 0.36 & 0.13 & \(-\)0.15 & 0.13 & 0.02 & 0.02 \\ _Staphylococcus chromogenes_ & 0.11 & \(-\)0.31 & 0.67 & 0.01 & 0.10 & 0.45 \\ _Staphylococcus haemolyticus_ & 0.33 & \(-\)0.31 & 0.14 & 0.11 & 0.09 & 0.02 \\ _Staphylococcus lentus_ & 0.18 & \(-\)0.46 & \(-\)0.46 & 0.03 & 0.21 & 0.22 \\ _Staphylococcus epidermidis_ 1 & 0.17 & 0.43 & \(-\)0.31 & 0.03 & 0.19 & 0.10 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Eigenvector spreadsheets and variable contribution based on correlations using principal component analysis (PCA) after air filtration with cloth, surgical, and filtering facepiece type 2 (FFP2) masks (_n_ = 396 [pooled data; 11 bacterial types \(\times\) 3 replication \(\times\) 3 masks \(\times\) 4 locations]) from locations A, B, C, and D in the three main components (p1, p2, and p3). was effective filtration of bacteria achieved with the FFP2 masks at locations B, C, and D and with the surgical masks at locations A, C, and D since the case data (masks used at locations) are clustered in the dark-colored area (between 40-100) and form the maximum on the 3D plot.