​​​Work in sewer / underground

​​​​​​​Do NOT go down in manholes that is not emptied and properly vented.
In manholes where there is sewage / wastewater, it can form dangerous gases that can make you faint. One must be two if you are going down a manhole, you also must use a harness that allows one to be pulled up again if you lose consciousness.

If you are going into a manhole that is not dangerous gases in you must:

Be two if you are going down a manhole, you must also use a harness that allows one to be pulled up again if you lose consciousness
One must also check there is nothing that could fall over when one go down and you have to be sure you know that there is not something dangerous in the sewer.

One should NEVER go down in a manhole if it is deeper than 3 meters.