A controlled discharge ostomy appliance assembly, comprising: (a) a controlled discharge ostomy appliance having a body-facing side for facing towards a stoma in use, the appliance comprising: a seal support wall; a flexible seal membrane sealed to the support wall to define a seal chamber; a resilient device disposed in the seal chamber and configured for generating, in response to compression of the resilient device from the body facing side, a resilient return force for urging the seal membrane in a direction towards the body-facing side to a deployed seal state; and at least one port communicating with the seal chamber for permitting the transfer of inflation fluid with respect to the seal chamber, said at least one port defining a fluid flow property to effect a dynamic damping characteristic for changes in volume of the seal chamber; and (b) a seal displacer fastened releasably to the appliance forming a combined assembly therewith, the seal displacer being manipulable by hand to displace the seal membrane against the return force of the resilient device, to place the seal membrane in a non-deployed seal state ready for the appliance to be fitted at a stoma, wherein in the non-deployed seal state the resilient device is substantially compressed, and the seal membrane is displaced to a substantially non-operative position, and whereafter, upon separation of the seal displacer from the appliance, the seal membrane advances progressively towards the deployed seal state by the resilient return force damped by the dynamic damping characteristic. (a) a controlled discharge ostomy appliance having a body-facing side for facing towards a stoma in use, the appliance comprising: a seal support wall; a flexible seal membrane sealed to the support wall to define a seal chamber; a resilient device disposed in the seal chamber and configured for generating, in response to compression of the resilient device from the body facing side, a resilient return force for urging the seal membrane in a direction towards the body-facing side to a deployed seal state; and at least one port communicating with the seal chamber for permitting the transfer of inflation fluid with respect to the seal chamber, said at least one port defining a fluid flow property to effect a dynamic damping characteristic for changes in volume of the seal chamber; and a seal support wall; a flexible seal membrane sealed to the support wall to define a seal chamber; a resilient device disposed in the seal chamber and configured for generating, in response to compression of the resilient device from the body facing side, a resilient return force for urging the seal membrane in a direction towards the body-facing side to a deployed seal state; and at least one port communicating with the seal chamber for permitting the transfer of inflation fluid with respect to the seal chamber, said at least one port defining a fluid flow property to effect a dynamic damping characteristic for changes in volume of the seal chamber; and (b) a seal displacer fastened releasably to the appliance forming a combined assembly therewith, the seal displacer being manipulable by hand to displace the seal membrane against the return force of the resilient device, to place the seal membrane in a non-deployed seal state ready for the appliance to be fitted at a stoma, wherein in the non-deployed seal state the resilient device is substantially compressed, and the seal membrane is displaced to a substantially non-operative position, and whereafter, upon separation of the seal displacer from the appliance, the seal membrane advances progressively towards the deployed seal state by the resilient return force damped by the dynamic damping characteristic.