ar - consists of several cancer-causing chemicals. When a smoker inhales cigarette smoke, 70% of the tar remains in the lungs. Try the handkerchief test. Fill the mouth with smoke, don't inhale, and blow the smoke through the handkerchief. There will be a sticky, brown stain on the cloth. Do this again, but this time inhale and the blow the smoke through the cloth, there will only be a very faint light brown stain.