I don't much condone the making of bho. It is dangerous, but it does work and it's one of the simplest extraction methods.
When I used to make mine I used 11x butane, great for torches too. Comes out super clean with the proper purge technique. I suggest doing it on a hot day outdoors with zero electronics nearby, nothing that could cause a spark. Better safe than sorry.
Member of the Month: July 2012, July 2014 - Nug of the Month: July 2012
I agree with Ganjagrowergu, Butane and Hydrocarbon volatile extraction is best left for the pros, as it is Extremely Dangerous. I don't condone BHO extraction unless you are using a closed loop system in a lab designed with all of the safety protocol in place. It is extremely dangerous to do open blasting with Butane or any flammable gas.
Too many people blow themselves up, endanger others because of butane extractions done in improper setups and environments. Plus using 100's of cans of butane is extremely wasteful to the planet.
I would instead recommend looking into Pressing Rosin, Oil extractions or water hash if you must make extracts.
IF you absolutely must use Butane, you may want to research "mystery oil" and "BHO" as most people that have used even pure butane have found a mystery oil residue left over which may be harmful. Also many commercially available cans of butane contain odorants which you do NOT want in you product. Professional labs do not use devices like this.
IF you decide to use this device, do it OUTDOORS, away from flames, heat, sparks, etc... Do NOT open blast indoors PERIOD! Remove any electronics from your pockets including cell phones, headphones, airpods, flashlights...etc... Butane is heavier than air and will gather in "pools" near the ground, and is undetectable to the nose if using pure butane which is why it should be done outdoors, or in a professional explosion proof lab.
Also, offgass your spent material (biomass) outdoors as it will still contain a lot of butane, and allow your "crude" to offgass outdoors as well. Butane has a fairly low LEL or Lower Explosive Limit therefore it doesn't take much to become an explosive mixture. (I think its about 1.7% volume of air to become ignitable)
BHO and hydrocarbon extraction is best left up to the pros who use closed loop systems, reviewed by engineers, using active explosion proof ventilation, gas detectors, automatic fire suppression systems in rooms that are designed to be explosion proof and intrinsically safe where all electronics are rated for use around explosive gasses (Class 1 Division 1).