Open blasting is a dangerous and unregulated method of extracting cannabis. An antiquated method of producing cannabis extracts, open blasting uses a flammable solvent in a glass or metal tube. Modern, regulated extraction methods may also use solvents but in a safe, sealed, closed-loop system operated by trained and experienced professionals. Due to the risk of explosion, open blasting is considered a potentially dangerous process. It's not legal and not used in commercial extraction facilities.
More about open blasting
Open blasting was popular in the early 1990s among hobbyists who used it to produce butane hash oil (BHO). Because the tubes weren't sealed and petroleum products like butane are flammable, accidents were bound to happen. Closed-loop systems used in professional facilities today are pressurized, allowing for more efficient extraction using less butane or other solvents.