By contaminated, I mean it has, in addition to butane, petroleum distillates, various thick oil based lubricants, and mercaptans mixed in it, none of which evaporates off or gets otherwise purged in the bho extraction process. These are all common additives to lighter butane, as they help with the functioning of the valves. Unfortunately, there is no regulation or oversight either here or internationally of butane purity, so butane manufacturers can disclose these additives or not and even lie about it on the labeling if they like. Since the boom in popularity of BHO there has been a rush of butane brands that have capitalized by selling cheap, impure, lube and mercaptan contaminated butane blends and labeling them as "Pure Butane", usually with some meaningless measure of purity like "5X refined", but as I said, there is no legal oversight as to such labeling claims. Vector is a popular brand that is highly contaminated. The big problem with this contamination is that there is no way to separate the contaminate from either the butane or your finished extract; butane dissolves lipids, the contaminates are lipids and so are the cannabinoids you want to extract. Once they are all mixed, its impossible to unmix (like trying to unmix a bottle of 50/50 canola/olive oil into light pure canola oil and dark pure olive oil, cant do it, they are too similar physically), and the contaminates themselves can cause lung, brain, and cardiovascular damage if vaped or smoked. You can easily test for these contaminates in your butane though, with a simple clean plate test - discharge the butane (or any solvent really) into a clear glass plate, let the butane evap (all this done outside, no sparks or flames), then allow the plate to come to room temp and the water condensate evap off, then smell it. If it smells like eggs, theres mercaptan contamination. Next, run your bare finger across it. If you feel greasy or slick, theres oil contamination. Around my way, seems everyone likes Vector, so I tested them, all 4 grades, and they all had equally huge amounts of oil contamination, over 10g a bottle! Turns out its popular round here bc it gives the highest amount of extract back - the kick though is the extract is half industrial lube, with no way to purify! I've never found a butane with a refinement number on the label that wasnt contaminated. Though sometimes I find other brands that have "pure" batches, the only brand Ive tested that is consistently pure butane (or at least a clean evaporating gas only) is Colibri. Its expensive, but with the jar method, you only need one can per oz herb. Check out the link in my sig for a full run down on BHO etc, and I have a list of confirmed contaminated and clean brands here:
https://www.rollitup.org/medicating/653906-clean-plate-test-how-check.html. Definitely ask if he does a clean plate test on his butane, and what brand it is. If the first answer is no, or if he uses on of the contaminated brands, stay away from his extracts!