The tritium-tracer technique has been applied for several years for studying water adsorption and desorption on surfaces. It allows quick and precise measurements of water coverages on technical surfaces at atmospheric conditions and offers ways to investigate potential techniques for reducing these mostly undesirable adsorbates. It has been found that, after thorough cleaning of technical surfaces (steel, aluminium, glass, quartz), water adsorption due to atmospheric humidity could be reduced to unbelievably low values. In this paper, data on water coverages versus cleaning procedures and residence times of water molecules on surfaces at ambient temperature are presented and discussed together with some reliability tests on this new method.