An ostomy appliance including: first and second walls connected to each other at or near their peripheries, the first wall having a stoma-receiving opening； a connection member connected to the first wall for attaching the appliance to a user； a waste collecting chamber defined by the first and second walls for receiving waste and/or gas from the stoma-receiving opening； a further chamber defined by at least third and fourth walls which are connected to each other； a gas opening provided in either or both of the third or fourth walls for permitting waste gases to pass therethrough from the waste collecting chamber； a gas vent for permitting gases in the further chamber to escape to atmosphere； and wherein movement of the first and second walls away from each other, as a result of waste or gases entering the waste collecting chamber, increases or at least maintains the volume of the further chamber.
