Nearly four years after Los Angeles County passed new requirements for pornographic performers, the porn industry has spread to nearby counties like Ventura County — and much of that filming is happening in residents' homes with or without their knowledge, the NBC4 I-Team has learned.

Private citizens believe their home is being rented out for a few days — perhaps never knowing it's become the set of a raunchy pornographic title.

An enema kit, bottle of lubricant and a business card are among the things Kristina Knapic said she discovered after renting her house out on the online rental service Airbnb.

Doing a bit of research, she learned the person who rented the house was Michael Lucas, an adult performer and producer, and owner of Lucas Entertainment.

A bit more digging revealed photos of her house — inside and out — posted on social media.

"They found a sex toy under one of the beds," said John Thyne III, one of Knapic's attorneys handling a lawsuit she's now filed. "They noticed some enema kits in the bathroom [and] some what turned out to be, I believe, male steroids in the refrigerator."

Thyne and attorney Lacy Taylor said Knapic contacted them with concerns the pornographic film could damage her house's image as a rental property.

"She feels violated," Taylor said.

"She's correct in saying that I didn't tell her," Lucas told NBC4.

Lucas said he's worked in adult film nearly 20 years, and using rentals for porn shoots is common.

"We rent houses all the time," he said. "Never did we run into this problem."

It happens enough that Thyne said he's spoken to at least two others who've had porn filmed at their houses but are too mortified to come forward.

"This is not an altogether uncommon practice," Thyne said.

Since LA's condom law went into effect in 2012, the porn industry has moved into neighboring counties like Ventura which requires a permit for every film production.

Not getting a permit is a misdemeanor and violators can be fined up to $1,000 and face up to six months in county jail. But the county said it has never prosecuted anyone.

The county told NBC4 if Lucas had filled out the permit application, the owner could have learned about the shoot before he filmed there.

"He knew that it wasn't OK or probably thought that it would not be OK and he wanted to hide that purpose," Taylor said.

Airbnb prohibits commercial filming without the consent of the host and agreed to pay Knapic's cleaning fees.

But Knapic is concerned about damage to her home's reputation, now suing Michael for a cut of the profits from his films.

"He's continuing to rent for this purpose and unless he's made to pay for doing this it, he'll continue to do it," Taylor said.

It's not the first time an Airbnb host discovered his home used for something raunchy.

"It doesn't shock me at all that this would happen," said Ari Teman of Manhattan, who rented out his apartment in 2012 only to learn the renter was advertising "XXX Freak Fest" there that night.

"You're basically saying, 'Yeah, sure, for a couple hundred bucks I'll let a complete stranger into my place," he said.

Asked about filming in it's rentals, Airbnb told us "This is extremely rare," but wouldn't tell us exactly how often it happens.

"We have zero tolerance for this type of behavior in our community, and we have permanently banned these guests from Airbnb," a statement emailed to NBC4 said.

Porn movie aside, Knapic's attorneys said it's the homeowner's right to know what happens at their own house.

"The use wasn't revealed before the rental," Thyne said, "and that's just not appropriate."

The Free Speech Coalition, a trade group which represents the adult industry, told NBC4 Airbnb is sometimes used by production companies.

"Some of the rental homes are professional film set rentals, but other are Airbnb or other rentals that may not be specifically equipped for adult," a spokesperson said. "People may not alert the homeowners, they may not pull permits, they may ask performers and crew to not talk about the film shoots."

The industry sees it as a result of L.A. County's recently passed laws.

"When you force the industry from a well-equipped infrastructure like the Valley, with not only traditional sound stages, but a large number of easily rented homes where adult filming is permitted and encouraged, and push it to the margins, and to area and locations where people are not aware that adult film is being shot, you're seeing the beginning of an industry moving underground," the spokesperson said. "Anytime you push workers into the shadows, you make their workplace more dangerous."

Airbnb said when someone has a negative experience, they work quickly to make things right.

Knapic's lawsuit has been moved to federal court because Lucas is a resident of New York.