# Bacteria Filtration Efficiency for Different Types of Protective Face Masks
## 3 Results and Discussion
from 60 (location D) to 100% (location C), _Microococcus_ spp. from 68 (location D) to 100% (locations A and B), and _S. chromogenes_ from 50 (location B) to 100% (locations A and D), with significantly different filtration efficiencies between individual locations (_p_ < 0.01). The filtration efficiency for _S. aureus_, _S. lentus_, and _S. epidermidis_ was 100% at all analyzed locations. FFP2 masks proved to be the most effective masks in filtering air, and the smallest differences in filtration efficiency were observed between the analyzed locations for individual bacteria. Thus, the bacteria _Corynebacterium_ spp., _S. aureus_, _S. lentus_, and _S. epidermidis_ were completely filtered at all analyzed locations (100%). Smaller oscillations in bacterial filtration efficiency were observed for _S. haemolyticus_ at 80 (location D) to 100% (locations B and C), _Bacillus_ spp. at 83 (location A) to 100% (locations B, C and D), _A. lwoffii_ at 94 (location D) to 100% (locations A, B and C), and _M. luteus_ at 96 (location A) to 100% (location B). The lowest efficiency of bacterial filtration with the FFP2 mask was achieved for _Microococcus_ spp. at 68 (location D) to 100% (locations A, B and C) and _S. chromogenes_ at 67 (location D) to 100% (location B). The abovementioned results collectively show that there are slight differences in the efficiency of the single-layer cloth mask filtration and it probably oscillates depending on the children's age between the groups and the health condition of the individuals present at each location spatially. Moreover, previous air ventilation of the indoor area and children's activity prior to the measurement might be important cause of some filtration differences measured within the bacterial strains. However, it is undoubtedly clear that this analysis has obtained results that confirm the efficiency of bacteria filtration increases from the single-layer cloth mask, which proved to be the least effective, to the surgical mask, to the FFP2 mask. In their investigation, [PERSON] et al. [24] also concluded that the filtration efficiency is different for various sizes of aerosols. This study showed that the single-layer cloth masks currently available for purchase had a minimum filtration efficiency of 50%. Our findings also support the recommendations from the WHO on the use of fabric masks [2]. Information on the bacterial growth of the collected microorganisms on tryptic soy agar (TSA), chromogenic BrillianceTM UTI agar, and blood agar is presented in Figure 4a-c. Meanwhile, the information for yeast and mold growth on the Sabouraud agar on a control air sample and samples filtered with single-layer cloth, surgical, and FFP2 masks is shown in Figure 4d. The first medium showed the growth of yeasts and molds on the control medium, as well as the growth under filtration with single-layer cloth, surgical, and FFP2 masks. In all tested locations and treatments, the highest colony growth was recorded in the control medium. Similar to what occurred with the chromogenic agar and TSA, a single-layer cloth mask proved to be the least effective in filtering yeasts and molds, while the surgical mask proved to be the second least effective. No yeast or mold colonies were recorded after the air was filtered with the FFP2 mask. To assess and further discuss mask filtration efficiency for yeast and molds, we have to point out the importance of the fit (which leads to gaps) while using the face mask [15]. The effect of gaps between the face and the mask as caused by an improper fit will affect the efficiency of any face mask for any microorganism. Harmful yeast and mold spores easily spread when there is a possibility of any gap. In order to determine the ability to retain bacteria, which included the efficiency of air filtration with single-layer cloth, surgical, and FFP2 masks at different locations, PCA analysis was used. A total of 396 pooled data sets were incorporated into the analysis (11 bacterial types \(\times\) 3 replications \(\times\) 3 types of masks used \(\times\) 4 locations).