put a hose on exhaust and run down in hole.
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this will work, lawnmower exhaust into hole, seal it and let it run a tank of gas out. 3/4" x 4 FT. range flex connector is great to hook to the exhaust opening, and easy to get down the hole. Of course black gas pipe will work too , but harder to "swing" around into the hole. -swing, 2 or 3 ells to swing into any position.