Gas molecule

Mean free path (λ) m

Pore radius (m)

Permeability (mol∙mm⁻²∙s⁻¹∙Pa⁻¹)

Ar

3.15E−04

4.72E−12

4.258E−08

He

3.63E−04

1.09E−11

5.253E−08

N₂

2.96E−04

4.45E−12

4.425E−08

CO₂

1.11E−04

2.22E−12

1.380E−08