Gas tight sewage pipe
Outgassing of flammable or explosive gases from the ground is a fact of life in former coal mining areas around the world. After coal mining has ceased and the mine workings have been ventilated, methane gas, for example, which is lighter than air due to its physical properties, strives to reach the earth’s surface via natural and artificial pathways. A critical gas-air mixture can form there under unfavorable conditions. In the worst case, deflagrations and explosions can be the result.
Rubber-sealed sewer lines are not gas-tight. To prevent ignitable mixtures from accumulating in the pipeline, many of these pipelines and shaft systems are welded together.