From practical experience from seeing the results, enough to level the house and have insulation falling out of the sky like snow a 1/2 mile away. See my previous post.
See my post just above, re: flamefront working to compress the un-ignited air/methane mixture (as the flamefront progresses forward). These ‘ignition’ events aren’t static things (there is forward momentum, and that is imparted to debris and walls as well as the pressure factor) ...
Also, did you see the Philly explosion? What was the wind like that night? 1/2 mile is not that far for debris in wind ...