An ostomy appliance comprising a front wall and a rear wall of flexible material, the rear wall having an opening into the bag by which waste material can enter the bag and one of the walls has one or more vents through which gas may escape from the bag and having a filter covering said vent, said filter...http://www.google.fr/patents/US6135986?utm_source=gb-gplus-shareBrevet US6135986 - Ostomy appliance
