Tobacco smoke that settles on indoor surfaces is called thirdhand smoke. It has pollutants that may cause health problems. The chemicals in thirdhand smoke include nicotine and cancer-causing substances such as formaldehyde and naphthalene.

Thirdhand smoke builds up over time. It can get stuck in soft items such as clothing, furniture, drapes and carpets. Thirdhand smoke also settles, like dust, on hard surfaces such as walls, floors and in vehicles. Thirdhand smoke can stay in place for many months even after you stop smoking.

By touching items or breathing in the gases thirdhand smoke may release, you can be exposed to those chemicals. Babies and young children who crawl and may put non-food items in the mouth are at higher risk than nonsmoking adults. They also tend to spend more time indoors.

Any indoor smoking raises the risk of contact with harmful chemicals. Secondhand smoke, from a tobacco product or the breath of a person using tobacco, causes many health problems. These can include cancer, heart disease and respiratory illness. The effects from long-term exposure to the toxins in thirdhand smoke are not as well studied.

You can’t get rid of thirdhand smoke with more airflow. Opening windows, using fans or air conditioners, or if you only smoke in certain areas doesn’t clear out thirdhand smoke. And it’s hard to clean off thirdhand smoke with typical household cleaning.

The only way to protect nonsmokers from exposure to secondhand smoke or thirdhand smoke is to remove all forms of smoking from indoor areas.

May 01, 2025

Original article: https://www.mayoclinic.org/healthy-lifestyle/quit-smoking/expert-answers/third-hand-smoke/faq-20057791