a mask with viscous porous resistance $C_{\mathrm{m}}=1000\, \mathrm{m/s}$[]{data-label="FIGFt0FgCm1000"}](images/Lg1Cm1000/compareFt-0.0005_Fg0Ft.png "fig:"){width="\factor\linewidth"}\
Flow rate $F_{\mathrm{t}}=95\, \mathrm{L/min}$\
![As Fig. \[FIGFt0Fg\], except for a mask with viscous porous resistance $C_{\mathrm{m}}=1000\, \mathrm{m/s}$[]{data-label="FIGFt0FgCm1000"}](images/Lg1Cm1000/compareFt-0.001583333_Fg0Ft.png "fig:"){width="\factor\linewidth"}

Flow rate $F_{\mathrm{t}}=30\, \mathrm{L/min}$\
![As Fig. \[FIGFt0FgCm1000\], except for logarithmic vertical axis[]{data-label="FIGFt0FgLOGCm1000"}](images/Lg1Cm1000/compareFt-0.0005_Fg0FtLOG.png "fig:"){width="\factor\linewidth"}\
Flow rate $F_{\mathrm{t}}=95\, \mathrm{L/min}$\
![As Fig. \[FIGFt0FgCm1000\], except for logarithmic vertical axis[]{data-label="FIGFt0FgLOGCm1000"}](images/Lg1Cm1000/compareFt-0.001583333_Fg0FtLOG.png "fig:"){width="\factor\linewidth"}

Flow rate $F_{\mathrm{t}}=30\, \mathrm{L/min}$\
![As Fig. \[FIGdp\], except for a mask with viscous porous resistance $C_{\mathrm{m}}=1000\, \mathrm{m/s}$[]{data-label="FIGdpCm1000"}](images/Lg1Cm1000/compareFt-0.0005_pm.png "fig:"){width="\factor\linewidth"}\
Flow rate $F_{\mathrm{t}}=95\, \mathrm{L/min}$\
![As Fig. \[FIGdp\], except for a mask with viscous porous resistance $C_{\mathrm{m}}=1000\, \mathrm{m/s}$[]{data-label="FIGdpCm1000"}](images/Lg1Cm1000/compareFt-0.001583333_pm.png "fig:"){width="\factor\linewidth"}

From Figs. \[FIGFt0Fg\]-\[FIGdpCm1000\], the analytical approach from Sect. \[SECtheory\] can be considered sufficiently validated. Therefore, Fig. \[FIGFt0FgLOGtheory\] presents analytical predictions without backup from simulation data. The figure shows that when the gap height is small (a few multiples of $0.1\, \mathrm{mm}$), then changing the seal thickness (i.e. the gap length) from a thin seal ($L_{\mathrm{g}}=0.1\, \mathrm{cm}$) to a wide seal ($L_{\mathrm{g}}=2\, \mathrm{cm}$) can change the gap flow rate $ F_{\mathrm{g}}$ by factor $10$ or more. This demonstrates that the thickness of the mask seal can have a substantial influence whether or not a mask fulfills FFP2- or FFP3-requirements.

Gap width $B_{\mathrm{g}}=2\, \mathrm{cm}$\
![Analytical predictions for the flow rate $F_{\mathrm{g}}$ through the 