A respiratory humidification system for providing heated and humidified respiratory gases to a patient, the system comprising: a liquid flow controller configured to provide a controlled flow of liquid for providing the humidification to the gases that pass through the respiratory humidification system; a heating system comprising a heater plate, the heater plate including a heating surface configured to receive the controlled flow of liquid and to heat the received controlled flow of liquid to provide humidification to gases passing through the respiratory humidification system, the heating surface including an evaporative area over which the controlled flow of fluid is distributed and vaporized by heat energy provided by the heating surface; one or more temperature sensors configured to measure a surface temperature of the heating surface; one or more hardware processors, configured to provide deterministic control of a humidity level of gases passing through the respiratory humidification system by instructing the liquid flow controller to adjust the controlled flow of liquid received at the heating system and instructing the heating system to adjust the surface temperature of the heating surface, wherein adjusting the surface temperature of the heating surface provides control to produce a known evaporative area; and one or more liquid sensors configured to detect whether the heating surface is wetted in at least one region; wherein the one or more hardware processors is configured to instruct the liquid flow controller to adjust the controlled flow of liquid received at the heating system and/or configured to adjust the operation of the heating system using the signal provided by the one or more liquid sensors; and wherein the one or more hardware processors is configured to generate an alarm and reduce the heat output of the heater plate upon the signal indicating an absence of liquid on the heating surface. a liquid flow controller configured to provide a controlled flow of liquid for providing the humidification to the gases that pass through the respiratory humidification system; a heating system comprising a heater plate, the heater plate including a heating surface configured to receive the controlled flow of liquid and to heat the received controlled flow of liquid to provide humidification to gases passing through the respiratory humidification system, the heating surface including an evaporative area over which the controlled flow of fluid is distributed and vaporized by heat energy provided by the heating surface; one or more temperature sensors configured to measure a surface temperature of the heating surface; one or more hardware processors, configured to provide deterministic control of a humidity level of gases passing through the respiratory humidification system by instructing the liquid flow controller to adjust the controlled flow of liquid received at the heating system and instructing the heating system to adjust the surface temperature of the heating surface, wherein adjusting the surface temperature of the heating surface provides control to produce a known evaporative area; and one or more liquid sensors configured to detect whether the heating surface is wetted in at least one region; wherein the one or more hardware processors is configured to instruct the liquid flow controller to adjust the controlled flow of liquid received at the heating system and/or configured to adjust the operation of the heating system using the signal provided by the one or more liquid sensors; and wherein the one or more hardware processors is configured to generate an alarm and reduce the heat output of the heater plate upon the signal indicating an absence of liquid on the heating surface.