A pressure swing adsorption apparatus for treatment of gases is disclosed. It includes a main inlet for receiving a flow of gas and one or more adsorption columns containing adsorption material. The columns are connected by a channel and the channel has an annular recess therein to receive a valve. The valve includes a support member formed from a pair of truncated cones and having slots extending therethrough. The valve also has a tubular membrane that surrounds the support member and is movable, in response to pneumatic pressure applied to the membrane, between a first position in which the membrane does not block the slots thereby allowing the gases to flow and a second position in which the membrane blocks the slots thereby preventing said gases from flowing through the valve.