Buying a used car is stressful. Much of this stress stems from the fear of taking a financial risk and buying a lemon, as well as being unsure of what the car went through before it was put up for sale. Getting an accident history can help reduce much of that concern. But accident histories do not account for how previous owners chose to “live” in their vehicles, such as whether or not someone previously smoked in the car. And this question is more important than you probably realize–both for your health AND the value of your car.

Smoking in a car—even if no one is inside with you while you’re smoking—still puts anyone who enters the car after the cigarette is out at risk of exposure to cancer-causing particles. This occurs through three steps.

• A standard car is a small, enclosed space. One cigarette smoked inside a car will not produce less cancer-causing particulars because the space is smaller. Instead, the same amount of particles are distributed across a smaller space. Therefore, smoking in a car leaves behind dense concentrations of tobacco pollution. Research has found that up to 90% of the toxic chemicals in tobacco smoke sticks to the surfaces inside cars.
• Most of the space in a standard car is made up of fabric/leather seats. Particles intobacco residue are easily absorbed into surfaces and are very sticky. These two characteristics makes smoking around fabrics to be especially dangerous. The seats in a car, which are already a challenge to clean, absorb and lock-in tobacco residue. Even with the top-of-the-line cleaning regiment, tobacco pollutants still remain in the car.
• Frequently getting in and out of cars activates particle movement causing toxic chemicals to readmit into the air. As people get in and out of cars, they cause the fabrics to shift. In that shifting, tobacco particles are readmitted into the air—even if you can’t smell them. These particles enter the human body through breathing and skin absorption. Once in the body, they begin to cause damage to your cells, DNA, and immune system.

Unfortunately, websites like Autotrader and Carmax don’t have a “non-smoking” search filter. This can make eliminating cars that have been previously smoked in challenging in online searches. Confirming that a car hasn’t been smoked in is best done by (1) talking to the seller and (2) inspecting the vehicle in-person.

It can be difficult to ask questions of people—but asking questions is how we get important information. Directly asking the seller if the vehicle has been previously smoked in is the first step. Ideally, the seller will be honest with you. But people often think they can hide a smoking history. Although it is difficult to confirm their story, you have the right to check for yourself.

Although a smell test is not a good indicator that a car hasn’t been smoked in, it is a starting point. If you smell smoke, the density of thirdhand smoke in the car is very high. It’s not even safe to sit in the car.

If you don’t smell smoke, your next step is to look around the inside of the vehicle for yellow-brown stains on the fabric–especially the carpeting on the roof. If you see this discoloration, the car has probably been smoked in.

Unfortunately, car cleaning companies are not equipped to fully remove thirdhand smoke pollution from vehicles. Although you could have the car detailed to remove the smell, depending on the concentration level, the smell will come back. But removing the smell doesn’t remove the health dangers affiliated with thirdhand smoke. So even if you commit to regularly getting your car detailed, you will still be exposed to odorless toxins every time you sit in your car.  Your best option is to not buy a used vehicle that you suspect was smoked in.

Buying a car remains stressful, but making sure the vehicle you buy is free from exposure to  cancer-causing tobacco particles will give you the peace-of-mind you need to feel comfortable sitting inside your own vehicle.