[Review of the development of air humidifiers working on the principle of evaporation with reference to their experimentally assured efficacy].

Basing on own measurements of the efficiency of customary water-bath humidifiers (humidifier of the ventilator RO-5 R, humidifier of the ventilator Engström ER 200, Bennett Cascade Humidifier, Hydrotrop 200 and Nicholas Humidifier) a critical review is given. As the results show only 3 of the humidifiers (Bennett Cascade Humidifier, Hydrotrop 200 and Nicholas Humidifer) make sure a really breathing air "conditioning" (moistening and rewarming). The humidifers of the ventilators RO-5 R and Engström ER 200 have only a very low efficiency, therefore they are not suitable for long term ventilation. Finally, the safety for the patient (the dangers of watercondensation, watertransport into the lungs, overheating, hypothermia and superhumidication) and the different expenditure of the clinical use of the humidifiers should be mentioned.