I have used alcohol and butane extractions. I did have access to a very professional lab set up, until my brother's death. I have been told by a professional chemist and a pharmacist, that even in a process without a complete lab , that does thoroughly allow the end product, to gas off , before using, that any traces left of butane is of little consequence to humans taking it internally . That family of gas, is not a threat to health internally, from tiny amounts that may be present in finished pot oil . Impurities in alcohol products or butane may be of more concern. Try to obtain the purest butane or alcohol that has no additives or was manufactured or mishandled or stored in improper containers. Butane often has scents added "as a safety factor" to make it easier to detect in the air we breathe. Evidently, various grain alcohols have not been scrutinized for what is left behind when evaporated in Pot oil. I use PGA or unscented butane. I am still walking and been using occasionally ,or frequently/daily, for 55 years, since my teenage years. Cigarettes kill much faster, so does excessive sugar and salt. The biggest danger from butane is stupidity and the ease of dangerous accidental explosions. Know your process, have the proper equipment and safe location/lab or leave it alone! Never use butane inside of a home! Always wear safety gear and have an extinguisher in your set up. I never had an accident and never took any chances with the process. Always in the lab or outside in an open area or under a shed with lots of moving air and safety precautions. Never use the butane process in a home! Gas flows under doors and settles into objects. Too many variables possible and too much at risk! PGA Alcohol and a vacuum pump with a stainless steel reactor/pressure vessel with a viewing port/window to observe the gassing process, chilled with dry ice and a solvent recovery system is best for me, but alas, I no longer have access to that lab set up or my brothers knowledge of the process. I provided the plant material and he the equipment and process expertise. Enjoy all of your concentrates more safely, as edibles! I use oil mostly for edibles these days. Heat Pressing buds for resin is a safe process, but smoking it is, likely, harmful to your lungs. But, it sure is good at getting one very stoned! 
I know this thread is old but if people still read it, it is still useful to post additions. I commented on the Butane pot oil processes ,years ago and got kicked off the site for a couple years. Indeed, it seemed all lab made concentrates were off limits, for a while if you gave any specifics of manufacturing them. Only simple stove top extracts were fair game then. I mentioned vacuum pumps, pressure vessels and super chilling and Bam! I was gone from here! Time has changed that apparently. I then, mostly, wanted to warn people about the danger of using butane without extreme care, while making high quality concentrates and how to make them safer.
