SAN FRANCISCO (CBS 5) – You’ve heard of the damaging health effects of smoking and secondhand smoke. But what happens when the smoke settles?

According to scientists, smoke literally sticks around for a while, as something they are calling “thirdhand smoke.”

Karolyn Ballard learned about it the hard way. Her new apartment had been painted and scrubbed, carpets cleaned. What she didn’t know was a heavy smoker just moved out.

“I woke up at night,” Ballard said, “and I could just smell the tobacco smell getting worse every night. It was like it was just oozing out of the walls.”

“It can be a real problem,” said landlord and professional ServPro cleaner Paul Watts. His crew wears protective gear to scrub a smoker’s house, to prevent nicotine poisoning.

“It’s a very long, slow process. And it has to be cleaned off before you can put paint, or else it’s going to bleed through the paint,” Watts said.

We’ve all smelled “thirdhand smoke” in places such as bars and stale hotel rooms. Now scientists are beginning to study it.

At Lawrence Berkeley National Laboratory, a chain-smoking machine puffs away on eight cigarettes at a time, depositing smoke residue on various materials so scientists can study the fallout and chemical reactions.

Researchers Mohamad Sleiman and Lara Gundel say nicotine is the gift that keeps on giving. The residue hangs around for weeks or months, they found, sticking to everything from clothes to carpets to kids — long after the smoker has gone.

“It’s really difficult to get rid of the smoke that is impregnated in the surfaces,” Sleiman said.

But that’s not all.

“What we have found is that residues of tobacco smoke will get more toxic with time,” said Gundel. More toxic as nicotine reacts with other household gases and chemicals, or gets taken into the lungs as dust.

“And those particles are teeny particles,” said Gundel. “And they’re very irritating. They’re more irritating than nicotine or cigarette particles themselves.”

In another groundbreaking study, San Diego State University professor Georg Matt tested apartments after smokers moved out and non-smoking families moved in.

“We find these compounds in some apartments, six months, maybe even a year or longer,” said Matt.

Even after the apartments were cleaned and painted, he found nicotine all over, including on the hands of non-smoking adults. Most disturbing, Matt said he also found signs of nicotine in the urine of children.

“This child, as well as the adults, are likely to get exposed to tobacco smoke that was smoked in that apartment months ago,” Matt said.

Scientists say children’s exposure to thirdhand smoke can be 10 times greater than adults’, because of their small size and their tendency to put things in their mouth.

“Our concern about children is that they can be exposed to these carcinogens through their skin and through breathing and eating dust,” said Gundel.

What are the health effects from thirdhand smoke? No one fully knows because it hasn’t been studied yet.

But researches such as Georg Matt say they do know this, “You can’t just open the window and it goes away.”

“When you live in an environment like this, you cannot escape it,” Matt said.

According to one experiment, even though airborne toxins from thirdhand smoke are about a hundred times less than from secondhand smoke, those exposures can add up over time.

CBS 5 asked tobacco industry leader Phillip Morris about thirdhand smoke. The company declined to comment.

(© 2011 CBS Broadcasting Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)