# Bacteria Filtration Efficiency for Different Types of Protective Face Masks
## 3 Results and Discussion
All mask application treatments at all locations showed statistically significant filtration efficiency compared with that of the control group (_p_ < 0.01). At location A, there was no statistical difference in filtration efficiency between the surgical and FFP2 masks (100% at both locations) or at location B between the single-layer cloth and surgical masks (79%). Further identification of yeast and mold species was not performed. Since the normal human flora consists various of Gram-positive and negative bacterial strains, it is not expected that there would be predominantly bacteria present in the air, especially indoors and during the summer season, when human skin is more exposed. It was assumed that the bacterial species of _Microoccus_ spp., _Staphylococcus_ spp., and _Bacillus_ spp. prevailed indoors. For this reason, detailed identification of bacterial species present at each location was made after air filtration with masks. _M. luteus_ was the most prevalent bacteria at all examined locations, followed by _Acinetobacter twoffi_ and _S. haemolyticus_ (Tables 2 and 3). \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline
**Bacteria/** & \multicolumn{6}{c}{**Location A**} & \multicolumn{6}{c}{**Location B**} \\ \cline{2-10}
**Treatment** & **Control** & **Cloth Mask** & **Surgical Mask** & **FFP2 Mask** & **Control** & **Cloth Mask** & **Surgical Mask** & **FFP2 Mask** \\ \hline _Acinetobacter_ & 61.33 & 42.33 \({}^{\text{A}}\) & 1.67 \({}^{\text{A,a}}\) & 0.00 \({}^{\text{A,a}}\)b & 21.67 & 8.67 \({}^{\text{A}}\) & 2.33 \({}^{\text{A,a}}\) & 0.00 \({}^{\text{A,a}}\)b \\ _Invoffi_ & (\(\pm\)2.52) & (\(\pm\)3.06) & (\(\pm\)0.58) & (\(\pm\)0.00) & (\(\pm\)1.53) & (\(\pm\)0.58) & (\(\pm\)0.58) & (\(\pm\)0.00) \\ _Bacillus_ spp. & 15.33 & 11.00 \({}^{\text{A}}\) & 1.33 \({}^{\text{A,a}}\) & 2.33 \({}^{\text{A,a}}\) & 6.67 & 2.00 \({}^{\text{A}}\) & 0.00 \({}^{\text{A,a}}\)a & 0.00 \({}^{\text{A,a}}\)a \\ _Crynebacterium_ spp. & (\(\pm\)1.15) & (\(\pm\)1.00) & (\(\pm\)0.58) & (\(\pm\)0.58) & (\(\pm\)0.58) & (\(\pm\)0.00) & (\(\pm\)0.00) & (\(\pm\)0.00) \\ _Crynebacterium_ spp. & - & - & - & - & - & - & - \\ _Microoccus_ & 136.67 & 128.67 & 12.00 \({}^{\text{A}}\) & 5.33 \({}^{\text{A,a}}\)b & 467.00 & 142.33 \({}^{\text{A}}\) & 19.67 \({}^{\text{A,a}}\) & 0.00 \({}^{\text{A,a}}\)b \\ _ luteus_ & (\(\pm\)6.11) & (\(\pm\)5.03) & (\(\pm\)1.00) & (\(\pm\)1.53) & (\(\pm\)9.00) & (\(\pm\)16.26) & (\(\pm\)1.15) & (\(\pm\)0.00) \\ _Microoccus_ spp. & 7.33 & 0.00 \({}^{\text{A}}\) & 0.00 \({}^{\text{A}}\) & 0.00 \({}^{\text{A}}\) & 1.00 & 0.00 & 0.00 & 0.00 \\ _Microoccus_ spp. & (\(\pm\)0.58) & (\(\pm\)0.00) & (\(\pm\)0.00) & (\(\pm\)0.00) & (\(\pm\)0.00) & (\(\pm\)0.00) & (\(\pm\)0.00) & (\(\pm\)0.00) \\ _Staphylococcus_ & 37.67 & 15.67 \({}^{\text{A}}\) & 0.00 \({}^{\text{A,a}}\)b & 0.00 \({}^{\text{A}}\)a & 3.67 & 0.00 \({}^{\text{A}}\) & 0.00 \({}^{\text{A}}\) & 0.00 \({}^{\text{A}}\) \\ _aureus_ & (\(\pm\)3.06) & (\(\pm\)0.58) & (\(\pm\)0.00) & (\(\pm\)0.00) & (\(\pm\)0.58) & (\(\pm\)0.00) & (\(\pm\)0.00) & (\(\pm\)0.00) \\ _Staphylococcus_ & 25.33 & 5.33 & 0.00 \({}^{\text{A}}\)a & 1.33 \({}^{\text{A,a}}\)b & 4.67 & 3.33 \({}^{\text{A}}\) & 2.33 \({}^{\text{A}}\) & 0.00 \({}^{\text{A,a}}\)b \\ _chromogenes_ & (\(\pm\)1.53) & (\(\pm\)0.58) & (\(\pm\)0.00) & (\(\pm\)0.58) & (\(\pm\)0. Interestingly, the presence of _M. luteus_ varied depending on the location, accounting for 40% of the total grown colony of all identified bacteria at locations A and C, while at locations B and D, this percentage was significantly higher at an average of 88%. _M. luteus_ are Gram-positive cocc usually found in soil and water resources and other natural environments. In addition, the species is also considered to be a normal inhabitant of human skin and orophnx mucosa [23]. This might be the reason for its greater prevalence at both school facilities, but this may also be the result of the filtration efficiency of the particular mask used for sampling. A slightly different situation was achieved with _A. luoffi_ and _S.