absolutely do it in the back yard, no doubt about it. and back away while its evapping, just in case! you do know that butane pools and sinks right? its heavier than air. you were definitely considered indoors, and just because the doors were open, were you getting proper ventilation, ie: intake and exhaust at the same rate for an efficient purge of the garages air? probably not.... so just start doing the spraying, and especially the evapping, in the middle of the yard, tons of ventilation. and dont stand aroud watching while it evaps... those fumes aint healthy to be breathing in, neither are flames. trust me, they fuckin hurt more than the average burn that youve prob had before! and when you go to the hospital, dont lie about it, tell them its a butane burn... we said it was gasoline so they gave my buddy a gasoline burn type cream that just made it worse, but then they might call the cops.. some places making BHO is like making meth. gets ya 10 years minimum. in cali I think its BRUTAL to get caught making BHO. kiss your family goodbye sorta thing. trust me, you dont want to blow up.
heat on low doesnt matter, a spark is a spark, live electrical is live electrical. all that butane needs is a microspark and then holy fuck watch out. even static sparks if youre wearing a big wool sweater when evapping can do it. or a cigarette butt sitting in the ashtray that you snuck in before the purge because ya just couldnt fucking wait 3 minutes (like my buddy) and only half assed put out by the back door, and youre evapping oil 15 feet away in the middle of the yard. gotta think about stuff before its too late. you got lucky, most explosions turn out pretty bad. depends how far into the cook you were I guess. I prefer all natural heat (warm water... or even sand) and ventilation (wind). takes 15 mins.. some members here just let theirs sit outside in the warmth for 6 hours, with no hot water below it.. im too impatient. the hot water makes it 100x more dangerous though, that butane evaporates QUICKLY.
winter dont matter, I live in canada and it was -41C last winter, its ALREADY winter here, we got snow this morning... no fucking joke. its +4C this morning... chilly out. the cold isnt a problem, just takes a few more water cycles is all.
take your butane dish, and find an even bigger one. now take that bigger one, fill it with hot water, set it in the yard... let your butane dish FLOAT in that hot water for 10 mins, and get the hell back into the house. then go check on it in 10 mins... 90% of the butane should be gone, and the water will be cold. set the butane dish down, go inside and get fresh hot water. back outside, let dish FLOAT in the hot water again for 10 mins... then its safe to bring inside and play with and finalize however you like.