i agree about the purging but I see oil that has been tested all the time here in Cali they test for butane thc content moisture fungus and sub cannibinoids. There's even this stuff called pure gold thc, they even extracted the chemical that causes dry mouth.It might evap, but the problem is the wax it can leave behind , nobody has ever tested butane in a edible/smokable way... i do know if i smoke to much my fuckin lungs arent so happy with me, i make sure i purge mine to , i refuse to smoke any oil asides from my own for that reason.