In a method and system of regulating multiple anesthetic agents in a breathing circuit of an anesthetic breathing apparatus is disclosed, a primary anesthetic agent added to the breathing circuit is regulated to a set desired value of the amount of the primary anesthetic agent, and a secondary anesthetic agent in the breathing circuit is regulated to an amount of said secondary anesthetic agent that it is equal to or less than a defined threshold level, e.g. of the concentration, of the secondary anesthetic agent.
