One of the main reasons this happens is due to overfilling or flooding the unit with e-liquid. One technique to try to correct overfilling is to hold a tissue or napkin over the threaded end of the cartomizer/Canteen™, then blow through the mouthpiece to clear any excess Smoke Juice. Be very careful NOT to inhale the e-liquid. If, for any reason juice accidentally gets into your mouth, spit it out immediately and rinse your mouth with water. If this is happening with a cartomizer, also make sure that the tip of the black rubber mouthpiece is correctly aligned into the air hole and is not sitting over the fiberfill.