^^^ Sounds like someone who shouldn't be using butane in the first place...
Great thread! I usually extract right by the front door, with it opened, and a large fan inside the house blowing outside. I also turn on the ceiling fans, just to make sure it doesn't have a chance to pool at all. I've done this literally hundreds of times safely, with no problems whatsoever. (Keep in mind, I'm a med patient in CO, not worried about someone walking up and seeing what I'm doing...)
In summer, it works even better to do it by the front door, as I turn on the swamp cooler, & it pressurizes the whole house. I close all the windows and doors except the one I'm extracting in front of, the pressure from the swamper pushes out everything QUICKLY (tested the air moving capabilities before I shot any tane with a burning joint, the smoke will give you a general idea of how fast the air is moving).
After I shoot the tane and 95% drips out (between 1-3.5 cans, depending on what size extractor I'm using), I take the tube and set it off in another pyrex dish, off to the side, so it can drip out whatevers left. I then take the dish with the butane, and place it into a waiting double boiler, still right by the front door, wide open. The butane is boiled off almost immediately at this point, during this whole time I'm extremely careful until the lions share of the butane is gone.
Once it's mostly gone, I'll leave it in the double boiler to purge, and leave the door open and fan on (or swamper on, depending on the season) for a while, just to make sure any residual is completely out of the house. No one smokes, walks or even farts while I'm shooting BHO, don't want any ignition sources, even the remotely possible ones like static. I don't close the door until 99% of the butane is gone, and only small bubbles of butane is all thats left.
This won't work for everyone, obviously, but it works well for me. Never liked extracting outside, always seems to be a bit of dirt or something that gets into the oil... YMMV.