Thirdhand smoke is the chemical residue from tobacco smoke. It is also called “tobacco smoke residue” or “stale tobacco smoke.” The chemicals in thirdhand smoke are toxic to humans, especially children. Thirdhand smoke can linger for years in dust and on household surfaces. It can also become embedded in carpets, furniture, clothes, and building materials. It is difficult and expensive to remove.

When people smoke in a car, thirdhand smoke residue builds up just the way it does in any indoor environment. However, a car is a much smaller space. When someone smokes in a car, the concentration of tobacco smoke chemicals can become much higher than in an office or apartment. This is true even if the car’s ventilation system is on or the windows are open.  A car’s interior contains more materials and surfaces, such as floor carpeting, seat fabrics, upholstery, and ceiling liners, that can absorb toxic tobacco residue. Once absorbed, these chemicals can be re-emitted into the air and settle in dust in the car. Even if a car’s interior is cleaned often, the tobacco residue will remain in reservoirs embedded in the fabrics and upholstery. In addition, even if someone smokes only outside of the car, they can transfer thirdhand smoke into the car on their hands, skin, hair, and clothes.

Before you “sign on the dotted line,” take these steps to help you determine whether or not a prior owner allowed smoking inside the vehicle: 

1. Ask about prior smoking in the vehicle 
Actively engage the seller in a discussion about prior smoking in the vehicle. If you are speaking with the owner, you can ask two simple questions:  

1. Did you smoke in this car?  
2. Did you let others smoke in this car?

Similarly, if you are speaking with a dealer you should ask:  

1. Did you ask the previous owner about smoking?  
2. If not, can you find out if the previous owner ever smoked or allowed smoking in the car? 
3. When you prepared the car for sale, did you notice any smell or other signs of tobacco use? 

Although asking is essential, it’s important to recognize that owners are not required to disclose previous smoking, and a dealer may know very little about the previous owners’ smoking history. 

2. Inspect the vehicle 
Get inside, close the doors and windows, and conduct your own inspection: 

1. First, smell. The odor of stale tobacco smoke means thirdhand smoke has accumulated in the vehicle.
2. Be cautious if you smell air fresheners or perfumed upholstery cleaners. It is not uncommon for a seller to use “air fresheners” or fragrances to disguise unpleasant odors.  If you smell fragrances in a used car, ask why the seller felt it was necessary to use them.  
3. Look for stains, another sign of tobacco smoking in the car. Check along the edges of car panels or the ceiling liner for discoloration. 
4. Check the seat covers and flooring for signs of small burns that could indicate accidentally dropped cigarettes or fallen ashes. 

3. Be cautious of a great deal 
If the price is “too good to be true,” it just might be. The resale value is lower for cars that have been smoked in. An owner or dealer might offer a low price in order to move the vehicle quickly. 

Do you have more questions about the toxic legacy of tobacco smoke, how it affects human health, and what we can do about it? Learn more here.

Updated: September 2023

Sources:

Continente X, Henderson E, Lopez-Gonzalez L. et al. Exposure to secondhand and thirdhand smoke in private vehicles: Measurements in air and dust samples. Environmental Research 2023; 235. doi: 10.1016/j.envres.2023.116681

Fortmann AL, Romero RA, Sklar M, et al. Residual tobacco smoke in used cars: futile efforts and persistent pollutants. Nicotine Tob Res 2010;12(10):1029-36. doi: 10.1093/ntr/ntq144 [published Online First: 2010/09/02] 

Matt GE, Fortmann AL, Quintana PJ, et al. Towards smoke-free rental cars: an evaluation of voluntary smoking restrictions in California. Tob Control 2013;22(3):201-7. doi: 10.1136/tobaccocontrol-2011-050231 

Matt GE, Quintana PJ, Hovell MF, et al. Residual tobacco smoke pollution in used cars for sale: air, dust, and surfaces. Nicotine Tob Res 2008;10(9):1467-75. doi: 10.1080/14622200802279898 

Matt GE, Romero R, Ma DS, et al. Tobacco use and asking prices of used cars: prevalence, costs, and new opportunities for changing smoking behavior. Tob Induc Dis 2008;4:2. doi: 10.1186/1617-9625-4-2 

Jacob P 3rd, Benowitz NL, Destaillats H, Gundel L, Hang B, Martins-Green M, Matt GE, Quintana PJ, Samet JM, Schick SF, Talbot P, Aquilina NJ, Hovell MF, Mao JH, Whitehead TP. Thirdhand Smoke: New Evidence, Challenges, and Future Directions. Chem Res Toxicol. 2017 Jan 17;30(1):270-294. doi: 10.1021/acs.chemrestox.6b00343. Epub 2016 Dec 21. PMID: 28001376; PMCID: PMC5501723.

Pitten, L., Brüggmann, D., Dröge, J. et al. TAPaC—tobacco-associated particulate matter emissions inside a car cabin: establishment of a new measuring platform. J Occup Med Toxicol 17, 17 (2022). https://doi.org/10.1186/s12995-022-00359-x