How to make your own e-liquid for your electronic cigarette. I purchased my nicotine base & PG at www.ecigexpress.com I bought my flavors and empty bottles at www.perfumersapprentice.com FREE calculator for e-liquid www.todmuller.com IMPORTANT FACTS*** Propylene Glycol USP grade is safe for human consumption, including inhalation. It is used as a germ killer in both solid and gas forms. Its in your prescription drugs. Its in your cosmetics.