**2. Medical mask**

4 Will-be-set-by-IN-TECH

Sample Description Measurement Number of Warp / weft

(a) Cotton woven fabric 160 – 20 452 22 / 21 (b) Thick monofila- 80 – 10 <sup>2200</sup> 55 / 40 ment fabric

(c) Multifilament 270 – 140 <sup>960</sup> 32 / 30 woven fabric

(d) Very thick monofila- 24 – 12 <sup>32400</sup> 180 / 180 ment woven fabric

Porosity test procedure Parameter Sample

Table 1. Samples used in the testing of J-method

Porosity parameters when the number of pores is known (the first procedure)

Porosity parameters when the number of pores is unknown (the second

procedure)

between the threads of warp and weft.

measurement on 50 pores of the sample (b).

interval [*μ*m] [pores per cm2] [threads per cm]

(a) (b) (c) (d)

*b* 0.5794 0.6355 0.8329 0.7174 *h* [*μ*m] 14 10 13 2 *m* 10 7 10 7 *nt* 452\* 2200 960 32400 *d* [*μ*m] 45.04 31.37 200.45 18.84 *dt* [*μ*m] 53\*\* 30 199 18.78 *P* [%] 0.98 2.07 31.32 9.06 *Pt* [%] 1.00\*\* 3.43 29.84 8.98 *a*<sup>0</sup> 9.4074 2.8236 0.28 0.8791

*d* [*μ*m] 45.00 32.77 *P* [%] 6.96 6.17 *n* 3314 6213 *a*<sup>0</sup> 1.28 1.28

*dt* [*μ*m] [*μ*m] [*μ*m] [*μ*m2] [*μ*m2]

Table 2. Parameters of porosity estimated with J-method for all four samples. \* - the number corresponds to the product of the warp and weft. \*\* - corresponds to the 452 measured pores - between the threads of warp and weft only one typical pore was measured in each void

Statistic parameters *<sup>w</sup> <sup>l</sup> dt Preal* <sup>=</sup> *w l Phydr <sup>l</sup>*

Mean 20.13 66.06 30.00 1364.67 786.29 2.50 Standard deviation 7.77 13.75 10.19 664.13 461.38 1.19 Minimum 4.76 23.81 8.82 287.12 61.07 1.04 Maximum 34.92 87.3 46.91 2519.68 1727.43 6.86 Total 68233.43 39314.56

Table 3. Results of the scanning-electron microscope pore's shape and open area

A medical mask fabric is composed of three layers. The outer layer and the layer suite on the face of a subject are composed of fibres which diameter is 18*μ*m. The inner layer is composed from microfibers which diameter is 2*μ*m, see figures 2 and 3. In this layer the fibres are arranged in 37 sub-layers.
