What is a one-sentence summary of the following article?
The smell of cigarette smoke is a scent that lingers and is hard to get rid of. If your teenager has been smoking, it is almost guaranteed that you will be able to smell it on their clothes or in their hair (especially if they have longer hair). Note: Sometimes teenagers try to cover up the smell of smoke by overcompensating with cologne or body spray. You will still be able to smell the smoke, but it might be partially masked by the perfume. Kids will often try to air out or vent their room by leaving the window open after smoking in their room. It might be normal for your child to want their window open, but pay special attention if they insist on doing it even when the weather is unpleasant (too hot, too cold, rainy, etc.). Teenage smokers are less experienced and have worse hand-eye coordination than adults. So, they are more prone to accidentally burning things if they start smoking. Watch out for burn marks on the carpet in their room or on their clothing. Also look for burn marks in their car, as many teens think they can mask the smell of the smoke more effectively in their car then in their room. It may be hard to notice these tiny objects, but if your teenager has recently started carrying around or purchasing lighters and/or matches, this may be a sign that they are smoking. They may claim that they only want it for lighting candles, but notice the frequency with which they use the matches or lighter to determine if you think they are smoking or not. Teenage smokers can be very persuasive, so other teenagers often succumb to existing peer pressure to smoke. Teens with friends who smoke are much more likely to start smoking than those without smoker friends. Smokers can be very conscious of the fact that smoking makes their breath smell distinctively like cigarettes. So they often try to counteract this effect by chewing gum or using mouthwash after smoking. If your child appears to be worrying to an extreme about how their breath smells, they might be trying to hide the fact that they are smoking from you. Smoking is an expensive habit. If you have access, check your teen's online bank account activity and see if they are making frequent purchases at convenience stores, grocery stores, or smoke shops. If they are buying cigarettes regularly, there will be a money trail for you to find.

Summary:
See if their clothes (or hair) smells like smoke. Notice if they start leaving the windows open in their bedroom. Look for burn holes in the carpet, in their car, and in their clothing. Watch out for matches or a lighter in their room or backpack/purse. Notice if they have friends who smoke. Pay attention if they start using mouthwash or gum more frequently. Check how they are spending their money.