All E-njoint™ oil cartridges are fully tested at the factory. The heating chamber is primed with a drop of 100% Food Grade Propylene Glycol (odor- and tasteless) to make sure the functionality and airflow of the product is according to E-njoint™ standards. Be aware that when you fill the E-njoint™ Revolution Cartridge with your oil, it might take 3-5 puffs before your oil reaches the heating chamber and the first few puffs might just be vape from the Propylene Glycol. Preheating the chamber will draw the oil towards the heating chamber. (2 clicks).