This simulation studies enriching the oxygen content of air with a single-stage membrane module. The binary mixture, A (O₂) and B (N₂), has an ideal separation factor, the ratio of the permeabilities of the two species, α* = 10. The permeability of oxygen is P_A = 500 x 10^-10 cm³ (STP)cm/(s cm² cmHg). The membrane is more permeable to oxygen and has a thickness t = 2.54 x 10^-3 cm. The stage cut, θ, is set by the user. The values of the pressures in the feed and permeate sides are chosen equal to P_f = 190 cm Hg and P_p = 19 cm Hg, respectively, which give a ratio of pressures, r, equal to 10. The feed rate and composition are given by: q_f = 106 cm³ (STP)/s, x_N2 = 0.791 and x_O2 = 0.209. This simulation computes the reject and permeate compositions as well as the membrane area. In addition, values of the local permeate compositions, both at the entrance and exit of the module, are given.