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Transcripción del abstract original del autor: The Danish gas companies have carried out a series of random sample inspections on approx. 500 domestic gas installations with balanced or split flues. The investigation showed that especially aluminium flues are likely to corrode, resulting in blockage and perforation. Flue pipes of stainless steel also showed signs of corrosion - pin hole - but not signs of blockage. A total of 11% of the inspected flues with incipient or serious corrosion and 22% with incipient or serious blockage was found. The primary cause of corrosion is sulphur compounds in the natural gas, which brings about condensation of sulphuric acid in the flue. In Denmark most of this sulphur comes from odorisation of the natural gas. In continuation of the random inspections a mathematical model was made to make further analyses. In particular, we were interested in the effect on corrosion of the way the boilers are operating. On the basis of the model calculations we concluded that acid will always develop in the standard flue (independent of the operation conditions) with an ensuing risk of corrosion. The sulphuric acid condenses and is concentrated in selective spots of the flue, depending on the flue design. Condensation of acid depends on flue length, number of bends and on gas consumption, whereas operation time of the boiler and intermittent operation seem to have no effect on the condensation of acid. It is estimated that there is a risk of corrosion or fouling of aluminium flues within 3 to 10 years of operation at standard conditions and with a typical natural gas consumption rate, depending on design and thickness of the flue.