## 3 Results  
The snow used during the experiment was classified as dry and moist snow of low density (150 \(\pm\) 5 kg\(\cdot\)m\({}^{-3}\)). The snow grain size was determined to be 1 mm (medium to coarse), and the snow hardness corresponded to soft snow (4F). The density of PD was 157 kg\(\cdot\)m\({}^{-3}\) with a porosity of 0.78 and a tortuosity of 0.92, and the density of the PW,prepared as a mixture of dry perlite and water in a defined weight ratio of 80:20, was 250-255 kg\(\cdot\)m\({}^{-3}\). Figure 2 illustrates the findings of the analysis of normalized concentrations of O\({}_{2}\) and CO\({}_{2}\) in S, PW, and PD materials after a diffusion time of 60 min. O\({}_{2}\) propagated faster than CO\({}_{2}\) in all materials. For S and PW, the concentrations of O\({}_{2}\) and CO\({}_{2}\) differed significantly throughout the cylinder, except for the first sampling point. For PD, there was a significant difference in concentrations of O\({}_{2}\) and CO\({}_{2}\) beginning 250 mm from the inlet chamber. When comparing the tested materials, O\({}_{2}\) propagated the fastest in PW, as shown in Figure 3. The rate of O\({}_{2}\) propagation in the snow was bordered by the rate of propagation in PW and PD from a distance of 300 mm from the inlet chamber. For CO\({}_{2}\), the differences were less pronounced between PW and PD than for O\({}_{2}\). The rate of CO\({}_{2}\) propagation in S was slower than in PW or PD. Figure 2: Normalized measured concentrations of O\({}_{2}\) and CO\({}_{2}\) related to the concentrations in the inlet chamber depending on the distance from the inlet chamber in S, PW, and PD. Symbol # indicates a statistically significant difference between O\({}_{2}\) and CO\({}_{2}\). The density of the snow, measured after the experiment, varied from 304 kg\(\cdot\)m\({}^{-3}\) (porosity of 0.66 and tortuosity of 0.87) at greater depths to 145 kg\(\cdot\)m\({}^{-3}\) (porosity of 0.84 and tortuosity of 0.94) at shallower depths. With the decrease in snow depth and density, the average DCs for O\({}_{2}\) and CO\({}_{2}\) increased on average up to 19 mm\({}^{2}\cdot\)s\({}^{-1}\) and 11 mm\({}^{2}\cdot\)s\({}^{-1}\), respectively, as shown in Figure 4.  
A comparison between the theoretically calculated and measured DCs of O\({}_{2}\) and CO\({}_{2}\) in S, PW, and PD is shown in Table 1. For S, the theoretically calculated DCs were  
Figure 4: The measured DCs for O\({}_{2}\) and CO\({}_{2}\) in snow depending on the distance from the inlet chamber. Figure 3: Measured concentrations of O\({}_{2}\) and CO\({}_{2}\) related to the concentrations in the inlet chamber depending on the distance from the inlet chamber in S, PW, and PD. Symbol # indicates a statistically significant difference between S and PD, symbol $ indicates a statistically significant difference between PW and PD, and symbol $ indicates a statistically significant difference between S and PW. 11.1-15.1 mm\({}^{2}\cdot\)s\({}^{-1}\) for O\({}_{2}\) and 8.7-11.9 mm\({}^{2}\cdot\)s\({}^{-1}\) for CO\({}_{2}\) depending on the snow density and environmental conditions. The decrease in snow density resulted in measured DCs for O\({}_{2}\) exceeding theoretical DCs. The measured DCs for CO\({}_{2}\) were in good agreement with the theoretically calculated DCs, except for the first two sampling points. The average ratio of DCs between O\({}_{2}\) and CO\({}_{2}\) was between 1.2 and 1.9. The measured DCs in PW, ranging from 22.2 to 29.5 mm\({}^{2}\cdot\)s\({}^{-1}\) for O\({}_{2}\) and from 11.5 to 15.3 mm\({}^{2}\cdot\)s\({}^{-1}\) for CO\({}_{2}\), largely exceeded the theoretically calculated DCs. On average, the ratio of DCs between O\({}_{2}\) and CO\({}_{2}\) was between 1.7 and 2.1. In PD, the theoretically calculated DC was calculated to be 13.8 mm\({}^{2}\cdot\)s\({}^{-1}\) for O\({}_{2}\) and 10.8 mm\({}^{2}\cdot\)s\({}^{-1}\) for CO\({}_{2}\).