A method and apparatus for treating gas for delivery into a body cavity, body space or body surface of an animal. The apparatus comprises a housing defining a chamber having an entry port and an exit port. One or more agents are released into the gas stream that flows through the chamber so that the gas stream carries the agent to the animal. Also shown, for use with, or without, the chamber, is an agent chamber adapted to be coupled to at least one structure defining at least one fluid flow path extending at least a portion of the distance between an insufflation device and the body cavity, body space or body surface.