## 4 Discussion  
The main finding of this study is that perlite in both forms (wet and dry) has similar diffusion properties for oxygen and carbon dioxide as the low-density snow used in this study. Oxygen diffused faster than carbon dioxide in all tested materials, consistent with the diffusion coefficients for both respiratory gases. S and PW exhibit similarly in terms of diffusion, with a marked difference between oxygen and carbon dioxide in both materials. In contrast, for PD the difference between O\({}_{2}\) and CO\({}_{2}\) is minimal but still statistically significant, as presented in Figure 2.  
We speculate that the greater difference between O\({}_{2}\) and CO\({}_{2}\) in PW and S compared to PD may be attributed to the absorption of CO\({}_{2}\) in the water present in these two materials. This is because the experiment was conducted at temperatures around 0 \({}^{\circ}\)C. The small difference in diffusion between O\({}_{2}\) and CO\({}_{2}\) in PD could potentially be attributed to the physical and chemical distinctions among the molecules. The effect of CO\({}_{2}\) solubility in water was also considered in the breathing experiments conducted by [PERSON] et al. [18], where the authors speculated that the snow surrounding the air pocket might act as a CO\({}_{2}\) buffer, owing to its 24-fold higher solubility of CO\({}_{2}\) in water compared to O\({}_{2}\)[26]. It is important to note, however, that the findings may have been different at lower ambient temperatures, as the absorption of CO\({}_{2}\) in ice is very low and almost unmeasurable, according to a study by [PERSON] et al. [21]. The equation published in the study by [PERSON] et al. [10] for estimating the theoretically calculated DC in snow was applied to PW and PD in this study. The measured DCs for both respiratory gases were twice as high as the theoretically calculated DCs when utilizing Equation (1) for PW. It can be speculated that this is due to water or ice in the PW causing clogging of the pores in the individual grains, resulting in the faster propagation of respiratory gas molecules around the individual grains. In PD, the measured DC for O\({}_{2}\) was about 1 mm\({}^{2}\cdot\)s\({}^{-1}\) lower (relative deviation up to 8%) than the theoretically calculated values, but the measured DC for CO\({}_{2}\) was in good agreement with the theoretically calcu \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multicolumn{2}{c}{**O\({}_{2}\) DC**} & \multicolumn{2}{c}{**CO\({}_{2}\) DC**} \\  & & **(mm\({}^{2}\cdot\)s\({}^{-1}\))** & **(mm\({}^{2}\cdot\)s\({}^{-1}\))** & **O\({}_{2}\)/CO\({}_{2}\) DC Ratio (-)** \\ \hline \multirow{2}{*}{S} & Theoretical & 11.1–15.1 * & 8.7–11.9 * & 1.27 \\  & Measured & 13.2 \(\pm\) 3.7 & 8.8 \(\pm\) 1.9 & 1.50 \(\pm\) 0.17 \\ \hline \multirow{2}{*}{PW} & Theoretical & 10.9 & 8.5 & 1.27 \\  & Measured & 25.8 \(\pm\) 2.5 & 14.0 \(\pm\) 1.0 & 1.85 \(\pm\) 0.14 \\ \hline \multirow{2}{*}{PD} & Theoretical & 13.8 & 10.8 & 1.27 \\  & Measured & 13.0 \(\pm\) 1.1 & 11.2 \(\pm\) 1.2 & 1.16 \(\pm\) 0.06 \\ \hline \hline \end{tabular}  
* Depending on the density.  
\end{table} 
Table 1: Theoretical and measured DCs of O\({}_{2}\) and CO\({}_{2}\) in S, PW, and PD. lated value. The measured ratio of DC between O\({}_{2}\) and CO\({}_{2}\) was found to be 1.16 \(\pm\) 0.06, which is lower than the theoretical value of 1.27. The measured DCs for both PD and PW remained unchanged throughout the entire cylinder, probably due to the compactness and incompressibility of the perlite. The DCs were notably highest in PW, with measured values up to 29.5 mm\({}^{2}\cdot\)s\({}^{-1}\) for O\({}_{2}\) and 15.3 mm\({}^{2}\cdot\)s\({}^{-1}\) for CO\({}_{2}\). The slight difference observed between PW and PD for CO\({}_{2}\) may have arisen from the potential absorption of CO\({}_{2}\) in the water present in PW. The density of the snow varied throughout the cylinder, possibly due to gravitational forces.