Gas pipes can explode

Gas explosion: Risk of explosion if the gas content is between 4.4 and 16.5 percent

Vienna. In order for a gas explosion to occur, as it probably took place on Wednesday in Vienna-Wieden, a certain gas-air mixture ratio is required. This is the case with natural gas, which consists primarily of methane, with a gas content between 4.4 and 16.5 percent. If this is achieved, it will be "very dangerous," said Anna Mauerhofer from the Institute for Process Engineering at the Vienna University of Technology.

If the gas concentration is below 4.4 percent, the mixture is too lean, if it is above 16.5 percent, the mixture is said to be too rich. The latter is present in the gas pipes, which prevents ignition. With a natural gas / oxygen ratio in the optimal range, an ignitable mixture, even the smallest ignition source is sufficient to trigger the explosion. The ignition temperature of methane at around 600 degrees Celsius is reached with a lighter, electric spark or a glowing cigarette, according to the APA researcher.

Odorless methane

Methane itself is actually odorless, so that a leak can be noticed at all, it is mixed with odorous substances, that is to say "odorized". A biomass gasification plant is also operated at the Institute for Process Engineering at the Vienna University of Technology. As in private households, it is also important to take appropriate safety precautions here. "Of course, maintenance is a very important point" - especially with older pipes, as the scientist from the research group "Gasification and gas cleaning" emphasized.

The guild master of the Viennese plumbers, Robert Breitschopf, told the APA that one can only speculate about any factors that led to the accident in Vienna's PreƟgasse. In any case, such a gas explosion is "extremely, extremely unusual. I have never experienced anything like it".

One factor could be that in such heat waves in densely built-up areas windows are usually kept closed during the day. If gas escapes from a thermal bath, it normally evaporates through the chimney. "If there is an ignition, there will be a deflagration in the chimney, but it does not wear the hut down," said Breitschopf.

Rather unlikely

The low pressure in the gas pipes itself also makes it unlikely that concentrations that can lead to such explosions will be reached at all. "Something gross must have happened," said the guild master. It is also possible that someone used a liquefied gas bottle for grilling. In any case, one has to wait for the results of the investigations. (apa)