"Don Foreman" wrote

The 95% oxy 5% propane subterranian boom works a lot faster. I
don't know why the mix is so oxygen-rich, but that seems to be what
works in practice. Ignition is done with a robust and fairly powerful
spark, a piezo-popper apparently is not sufficient.

I'm working on such a device as we speak. I already have a couple of local
ranchers interested in seeing it when I get it working. Hey, I'll trade you
some steaks for rodent eradication ...................

Steve