Humidification and heating apparatus preferably including a spirally wound resistance-heated plate with its axis vertical and one side in thermal contact with a sheet of water absorbent material. Both plate and material are partially immersed in water in a tank the lid of which is sealingly engaged with the spiral plate. When used for artificial respiration air from a respirator is admitted and discharged from the tank at points such that it must travel along the spiral passage formed by the plate, water surface and lid thus picking up heat and water vapor to emerge preferably substantially saturated at a temperature which does not exceed the maximum desired input temperature at the patient. To prevent condensation en route to the end user, sufficient further heat is imparted to balance that lost in passage. Preferably the interconnecting apparatus between the humidifier and patient is heated at least in portions along its length and preferably by electrically heated elements embedded in the wall of the usual flexible tube leading from the humidifier to the patient.

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