Its easy actually. A bic lighter has enough butane to equivilate it to a 1/4 stick of dynomite. A poorly designed butane hash lab can easily go volatile and explode. There were so many houses being blown off their foundations out here in Colorado between 2015 and now, from people illegally blasting hash.
I am highly against open air blasting as it is just as dangerous as indoor. I wish people would take down instructional videos on youtube because if you don't understand basic chemistry you have no business blasting with butane. It is extremely dangerous not only to yourself but everyone around you.
The state of Colorado has very strict rules for designing, building, and operating a legal hash lab, which includes inspections by engineers and the fire marshal. My friend got involved in a BHO lab and went to prison for 2 years after the DEA kicked in his door in 2016 here in Colorado.
It's not a joke, butane blasting is extremely dangerous.
I think it's a felony now to even have the equip without a license. Not 100% on that tho.