"A person walks down stairs in their house and the tobacco odor is still there from the party the night before and they say...what they're smelling is third-hand smoke," scientist Lara Gundel said.
It is the smoke that clings to clothes, furniture and walls long after a cigarette has been put out.
The study released Monday by the Lawrence Berkeley National Laboratory found that third-hand smoke is especially dangerous when nicotine comes into contact with a common indoor pollutant typically found in household gas appliances. Vehicle engines also emit the same toxin.
The combination clings to walls, floors, carpets, drapes and other furniture and can last for days, weeks or months, the study concluded. Third-hand smoke also absorbs onto solid surfaces, including stainless steel interior parts of a car.
Opening a window or turning on a fan to ventilate a room will not help much either, the study found.
"If you can smell it, it's still there," Gundel said.
And while smokers are putting themselves at risk, the study determined that third-hand smoke poses the greatest hazard to toddlers and infants because their skin and clothes regularly come into contact with smoke-absorbed carpets.
If you have to smoke, researchers say do it outside.
Even if until today many did not know the scientific definition of third-hand smoke, many smokers had a feeling it could not be any good.
"My mom tells me about that all the time, but she doesn't call it third-hand smoke, she calls it nasty," Berkeley resident and smoker Jimmy Toney said.