Closed-loop extraction
From Wiki Weed
Chemical extraction (whether using a hydrocarbon solvent or CO2) using a closed system, which means that the machine recycles the solvent rather than dispersing it in the air. Most commonly this is referring to a butane or propane extraction, but technically CO2 extraction machines are also closed-loop. A closed-loop system is much safer than traditional “open blasting” methods, and as such are now required for all legal concentrate production in Colorado.
