as the density required to be released in the crankcase is small, and should not acquire such as to be ignitable,
Scott.
All joking aside, this process does work, WITH PROPER TECHNIQUE, of coarse. If one wishes to test functionability (word?), first test, leave P.C.V. system intact, note effect, you will realize that only a small amount of butane is necessary, and particularly with a vacuum leak drafting the crankcase, no great sum is allowed to accumulate; with this familiarization then proceed.
O.K, so perhaps O.S.H.A. wouldn't approve; after all, "strike-anywhere" matches were replaced by "safety-matches", as some individuals just shouldn't be allowed to play with matches!
And, you can trust me, as I'm also a guy who when mounting BIG truck tires and it comes time to "blow em up", the initial inflation and seating of the bead is accomplished with the use of acetylene and a match....., it works every time...., KABOOOM!
Scott.
BTW: If you do screw-up and singe something, don't get pissed-off at me; you perhaps should not be allowed any matches!