GAS SEPARATION METHOD

Provided is a method for separating a specific gas from a raw gas using a gas separation membrane module. The module includes a gas separation membrane element enclosed in a housing. The element includes a gas separation membrane including a hydrophilic resin composition layer for selectively allowing for the permeation of the specific gas. The method includes the steps of: preparing the module; increasing pressure in an interior of the module; increasing a temperature in the interior; and feeding a raw gas to the interior. The hydrophilic resin composition layer of the module prepared in the preparation step is adjusted to contain moisture, and a moisture content thereof is an amount that allows an equilibrium relative humidity at a temperature of 23°C of a gas phase portion in the housing to be greater than or equal to 10%RH. The raw gas feeding step is performed after the preparation step. The pressure increase step and the temperature increase step are performed after the preparation step and before the raw gas feeding step.