| Study | Data | Source | Adaptation |
| Maclntyre et al. | Relative risk | Table 2 | |
| Filtration efficacy | Last paragraph of Results section | Calculated from penetration |
| Chughtai et al. | Percentage of compliance | Table 2 | |
| Risk ratio from multivariate analysis | Table 3 | |
| van der Sande et al. | Inward filtration efficacy | Table 2 | Calculated from penetration factor |
| Rengasamy et al. | Filtration efficacy | First paragraph of results section | Calculated from penetration level |
| Davies et al. | Filtration efficacy | Table 4 | Calculated from colony forming units |
| Shakya et al. | Filtration efficacy | Figure 2 & 5 | Graph digitization |
| Neupane et al. | Filtration efficacy | Section: filtering efficacy | |
| Konda et al. | Filtration efficacy | Table 1 | |
| Leakage | Conclusion | |
| Ma et al. | Filtration efficacy | Table 2 | |
| Cooper et al. | Leakage | Table 3 | |