A breathing assistance system (1) for delivering a stream of heated, humidified gases to a user for therapeutic purposes, comprising； a humidifier unit (21) that has an inlet port and an exit port, said humidifier unit adapted to in use receive a flow of gases from a gases source via said inlet port, said humidifier unit further adapted to hold and heat a volume of water in use, in use said flow of gases passing through said humidifier unit and becoming heated and humidified, said heated humidified gases exiting said humidifier unit via said humidifier unit exit port, a delivery conduit (6) and user interface configured to in use receive said heated humidified gases from said exit port for delivery to said user, said delivery conduit having a heater wire adapted to heat the gases within said conduit, a patient end temperature sensor (15) adapted to measure the temperature of said gases flow at or close to said patient, a flow probe adapted to measure the actual flow rate of said gases steam through said system, said breathing assistance system further comprising a controller adapted to receive data from said patient end temperature sensor relating to the measured temperature, and data from said flow probe relating to said actual flow rate, said controller determining a control output in response, said control output adjusting the power to at least said heater wire to maintain or alter the temperature of said flow or gases within said conduit to achieve a desire patient end temperature at said interface (7).
