The extraction of the active compounds in cannabis plants is conducted using equipment called a closed-loop system. The solvents used in the extraction process are entirely closed-off from the external environment. The solvents complete a circuit from liquid to gas to liquid again during the procedure. The closed-loop system is a fairly simple yet highly efficient and safe process.
While the type of solvent used may vary, the structure of a closed-loop system remains the same. There are three vessels, one contains the solvent, the other the plant material and the third collects the final extract. In order to collect all the therapeutic elements within a plant, the solvent may need to take several loops.
Irrespective of the solvent used, it must always be in liquid form. The solvent is allowed to pass over the plant material to dissolve the essential elements within it. The liquid runs off into the final tank and heat is then used to evaporate the solvent, leaving behind pure cannabis extract. The solvent which is now in gas form may be recycled and used on a new batch of cannabis.