A breathing circuit for the delivery of heated, humidified gases to a patient for medical purposes, comprising: a humidifier chamber adapted to hold a quantity of water and having an inlet and an outlet to allow gases to flow through said humidifier chamber, a blower unit adapted to in use deliver a stream of pressurised gases to the inlet of said humidifier chamber, a control system configured to adjust one or more output parameters of said breathing circuit, a heater plate which in use is located adjacent to said humidifier chamber and which is adapted to heat said quantity of water in said humidifier chamber so that said gases flowing through said chamber become heated and humidified, a gases transportation pathway connected to said outlet of said humidifier chamber to convey said gases flow to said patient, said gases transportation pathway having a patient interface adapted to supply said patient with said gases flow, characterised in that said gases transportation pathway also has an RFID tag located at or close to the patient end of said gases transportation pathway, said RFID tag adapted to sense a parameter of said gases passing through said gases transportation pathway, and wherein said RFID tag is configured to act as a breathing circuit component identifier, said control system also having an RFID interrogator adapted to interrogate and receive data from at least one RFID tag in real time, said RFID interrogator receiving data comprising that relating to said sensed parameter and the RFID tag component identifier, said control system adjusting the output parameters of said breathing circuit according to said received data. a humidifier chamber adapted to hold a quantity of water and having an inlet and an outlet to allow gases to flow through said humidifier chamber, a blower unit adapted to in use deliver a stream of pressurised gases to the inlet of said humidifier chamber, a control system configured to adjust one or more output parameters of said breathing circuit, a heater plate which in use is located adjacent to said humidifier chamber and which is adapted to heat said quantity of water in said humidifier chamber so that said gases flowing through said chamber become heated and humidified, a gases transportation pathway connected to said outlet of said humidifier chamber to convey said gases flow to said patient, said gases transportation pathway having a patient interface adapted to supply said patient with said gases flow, characterised in that said gases transportation pathway also has an RFID tag located at or close to the patient end of said gases transportation pathway, said RFID tag adapted to sense a parameter of said gases passing through said gases transportation pathway, and wherein said RFID tag is configured to act as a breathing circuit component identifier, said control system also having an RFID interrogator adapted to interrogate and receive data from at least one RFID tag in real time, said RFID interrogator receiving data comprising that relating to said sensed parameter and the RFID tag component identifier, said control system adjusting the output parameters of said breathing circuit according to said received data.