No SPRK will cause THRM to explode, unless the medium for the SPRK is wired to an ETRD with ports on either side of said THRM. Or if it's wired to an e-wall holding heated material, e.g. LAVA or FIRE, where the disabling of the e-wall will cause the said material to fall onto the THRM in question, but aside from those, and a few other semi-complex scenarios, SPRK directly applied to THRM will not detonate the THRM.
Dragonfree97 easiest solution (for me) Make box of RBDM and make a hole which has metal going in and fill the box with NITR and the rest is thermite.. simple
I made one, it's a BMTL ring 96 px in diameter, with a thickness of 4 px, add one part of C-4 right at the bottom, the rest is THRM, attach a lead from the top upwards or to where ever, spark, and boom! Here it is:
LoadSaveBlock(95714);
Very effective on cities, that save titled 'War' by I think it was wikku, which has metal planes and ships and stuff, and the like.