A humidifier for humidification of air to be delivered to a patient's airways may include a humidification chamber, a reservoir and a water delivery mechanism. The humidification chamber may include a water retention feature such as a wick that encloses part of the flow path, a heating element for heating the humidification chamber, and an air flow baffle configured to promote humidification. The humidifier may be further configured to execute one or more algorithms, for example to determine a condition of the wick or to detect condensation in the flow path. In some forms, the humidifier may also comprise algorithms for controlling one or more components of the humidifier such as to control the build up of foreign matter on the wick.