Particularly in states that have legalized recreational marijuana use, there has been an increase in production of marijuana extract, usually called hash oil, in the past few years, causing concern among law enforcement personnel, as discussed in a recent piece by USA Today and one from its affiliate, Statesman Journal. Hash oil is made by pouring a solvent (often butane) over marijuana leaves. The mixture is then heated, to evaporate the solvent. Users like this process because it allows them to create the much more THC-potent oil from what otherwise would be unusable parts of the plant. The potential danger comes from the fact that butane sinks; it is heavier than air and will descend, where stove pilot lights or even the motors in refrigerators can ignite it. People also store hash oil in their refrigerators, where the butane continues to evaporate, which can create flammable build-ups of the solvent.
In addition to its explosive potential, hash oil often has residual butane, as well as the lubricants used to ensure butane moves smoothly through lighters. It can also often contain pesticides (which are more concentrated than when found in marijuana that is smoked), and plant waxes that may be safe to eat but are not considered safe to inhale. Plus, even in most places that allow recreational marijuana use, it is still illegal to produce hash oil. A recent profile by BuzzedNews provides an in-depth discussion of the drug’s potential hazards.