The following techniques either do not work or are not effective in controlling moles.

Gas bombs, car exhaust, etc.:
The problem with these techniques is that the tunnel system is too large to accept the gas properly. It is like breathing through a straw that is 100 feet long. It just won't work. Plus the gas keeps getting siphoned off into the surrounding soil reducing the chances that the gas has reached a level toxic enough to kill a mole.

Flooding with a garden hose:
This technique has the same problem as gas bombing. While river like floods, do kill a lot of moles, it is not efficient to do that much flooding with a garden hose.