What is MTL Vaping? What Does Mouth to Lung Inhaling Mean? Young man gamer inhaling of a vapor with electronic cigarette.Vape flavor liquid chemicals.Use of e cigarettes in the home.Smoking and vaping negative Stock Photo Alamy If you vape, you inhale a lot of harmful substances. These can damage your heart and lungs. Vaping is especially harmful to individuals under the age of 25, as their brains are not yet fully developed. The chemicals found in vapes can cause problems with memory and retaining information,