I've never tried this ----- so it is just an idea.
Get a small engine like a lawnmower engine. Hook up some metal flex tubing and run the exhaust up the hole. Fill the gas tank and put just a pinch of 2 cycle oil in the gas tank. Maybe a 300-1 ratio (chanisaw normally 40 or 50 to one)Run the engine exhaust into the tunnel for a while with engine running at full throttle.
Maybe the carbon monoxide will do them in. Or at least chase them out.
Car or pickup exhaust might work too. Don't put oil in gas though. Garages use exhaust flex hose to pipe exhaust out of the mechanics buildings, so should be available. Use gloves - don't burn yourself on the pipe.
Probably something illegal about it though. Almost everything is any more.
Last edited by snrub; 01/23/15 01:38 PM.
