by Stephanie Diani for The New York Times

Lights, Camera, Actors ran their lines on the set of a pornographic film.

First, they show each other their cellphones: Each has an e-mail from a laboratory saying he or she just tested negative for H.I.V.syphilis,chlamydia and gonorrhea.

Then they sit beside the film’s producer, Shylar Cobi, as he checks an industry database with their real names to confirm that those negative tests are less than 15 days old.

Then, out on the pool terrace of the day’s set — a music producer’s hilltop home with a view of the Hollywood sign — they yank down their pants and stand around joking as Mr. Cobi quickly inspects their mouths, hands and genitals for sores.

“I’m not a doctor,” Mr. Cobi, who wears a pleasantly sheepish grin, says. “I’m only qualified to do this because I’ve been shooting porn since 1990 and I know what looks bad.”

Bizarre as the ritual is, it seems to work.

The industry’s medical consultants say that about 350,000 sex scenes have been shot without condoms since 2004, and H.I.V. has not been transmitted on a set once.

Outside the world of pornography, the industry’s testing regimen is not well known, and no serious academic study of it has ever been done. But when it was described to several AIDS experts, they all reacted by saying that there were far fewer infections than they would have expected, given how much high-risk sex takes place.

“I don’t think there’s any question that it works,” said Dr. Allan Ronald, a Canadian AIDS specialist who did landmark studies of the virus in prostitutes in a Nairobi slum. “I’m a little uncomfortable, because it’s giving the wrong message — that you can have multiple sex partners without condoms — but I can’t say it doesn’t work.”

Despite the regimen’s apparent success, California health officials and an advocacy group, the AIDS Healthcare Foundation, are trying to make it illegal to shoot without condoms. They argue that other sexually transmitted diseases are rampant in the industry, though the industry trade group disputes that.

In January, the city of Los Angeles passed a law requiring actors to wear condoms. A measure to do the same for the whole county is on the ballot on Nov 6.

Producers say the condom requirement will drive them out of business since consumers will not buy such films. Local newspapers like The Los Angeles Times oppose the ballot measure, calling it well-intentioned but unenforceable, and warning that it could drive up to 10,000 jobs out of state.

Very frequent testing makes it almost impossible for an actor to stay infected without being caught, said Dr. Jacques Pepin, the author of “The Origins of AIDS” and an expert on transmission rates. “And if you are having sex mostly with people who themselves are tested all the time, this must further reduce the risk.”

When the virus first enters a high-risk group like heroin users, urban prostitutes or habitués of gay bathhouses, it usually infects 30 to 60 percent of the cohort within a few years, studies have shown. The same would be expected in pornography, where performers can have more than a dozen partners a month, but the industry says self-policing has prevented it.

“Our talent base has sex exponentially more than other people, but we’re all on the same page about keeping it out,” said Steven Hirsch, the founder of Vivid Entertainment, one of the biggest studios.

Performers have to test negative every 28 days, although some studios recently switched to every 14.

If a test is positive, all the studios across the country that adhere to standards set by the Free Speech Coalition, an industry trade group, are obliged to stop filming until all the on-screen partners of that performer, all their partners, and all their partners’ partners, are found and retested. In 2004, the industry shut down for three months to do that.

It has had briefer shutdowns in each of the last four years.

In 2009 and 2010, no other infected performers were found. Coalition representatives said an infected woman in 2009, from Nevada, may have had an infected boyfriend, and offered evidence that a man infected in 2010 in Florida had worked outside the industry as a prostitute. The 2011 test was a false positive.

A shutdown in August came after several actors got syphilis, not H.I.V. All performers were given a choice: Take antibiotics, or pass two back-to-back syphilis tests 14 days apart.

State law in California covering these issues is vague. It requires protective gear for workers exposed to blood-borne diseases, but it was written with nurses and police officers in mind and does not mention condoms.

The California Occupational Safety and Health Administration interprets the law as requiring condoms, but says it cannot find the industry’s workplaces — most movies are shot in houses rented for a few days. Even if it does, it cannot enter without the producer’s permission or unless a performer files a complaint, which would allow investigators to get a warrant, said Amy Martin, the agency’s chief counsel.

But the industry hires only actors willing to work without condoms, so complaints are not filed.

The industry says the state’s interpretation would require all films to be shot with latex gloves, face shields and lab coats. It also says the state tolerates other industries, like boxing and football, in which performers take risks.

The Legislature has avoided making the law specific to pornography.

“No politician wants to touch the issue, because it’s about sex,” said Michael Weinstein, head of the AIDS Healthcare Foundation, who has made the issue a personal crusade.

For producers, it’s really about money.

Vivid Entertainment shot with condoms for two years after a 1998 H.I.V. outbreak, and sales dropped 30 percent, Mr. Hirsch said. Producers have threatened to leave the state, taking the jobs of 1,200 actors and more than 5,000 crew members with them.

Because of court rulings, filming adult movies is legal in California, Florida and New Hampshire. Nevada, where prostitution is legal, tolerates it.

Gay pornography, by contrast, has included condoms since the 1980s, because producers assume some actors are infected and because many gay men consider forced testing an invasion of privacy.

However, that is changing as “bareback” films become more common. Some producers claim their actors are safe because they shoot in places like Slovakia, where H.I.V. rates are very low, or because they test, or because infected actors are taking antiretroviral drugs, which can reduce the risk of transmission by 96 percent.

But it remains controversial. Chi Chi LaRue, who has been producing gay pornographic movies for 28 years and shoots only with condoms, dismissed bareback producers as “industry pariahs.”

While cases of H.I.V. are rare, Mr. Weinstein and California health officials say they also want condoms required to stop other diseases.

Thirty-five diseases — including drug-resistant gonorrhea — can be transmitted sexually, and the industry tests for only four, said Dr. King Holmes, head of global health at the University of Washington.

Los Angeles County officials estimated that sex-film actors get chlamydia and gonorrhea at least eight times as often as other young adults. The industry disputes that estimate, but a new study by the county suggests that the industry’s urine testing for gonorrhea underestimates how much is transmitted through oral and anal sex.

Actors insist that they are careful because their jobs depend on it. Top performers can earn $200,000 to $400,000 a year.

“If I get gonorrhea, we have to cancel the shoot, the crew is angry at me, and that’s unprofessional,” said Stoya. “And besides, it’s gonorrhea — yecch. So I use condoms in my personal life.”

Her co-star, Mr. Deen, concurred: “If I’m having sex off camera for fun, and it’s not someone from the industry who tests all the time, then it’s condoms, condoms, condoms all the way.”

Several working and former actresses interviewed said they opposed condoms for another reason: They chafe.

Actors repeatedly stop and start while lights and camera angles are changed and different versions of scenes are shot.

“The average length of intercourse for most Americans is 10 minutes,” said Nina Hartley, a former nurse and well-known actress in pornographic films since 1984. In her work, she said, “it’s 30 to 60 minutes of thrusting. It doesn’t matter how much lube you use, it’s uncomfortable, it’s a friction burn, and it opens up lesions in the genital mucosa. I could handle two to three condom scenes a month. But actors are paid by the scene, and I couldn’t do three in a week.”

Actors in Pornographic Films Fight Proposal to Enforce Safety Regulations

IMG_0413The California pornographic film industry turned out in force on Feb 18, 2016 to oppose regulations that would have forced actors to wear condoms and, in some cases, goggles, face shields or rubber gloves when on camera.

A parade of actors — fully dressed, and some colorfully so — took to the podium in a government auditorium here as five members of the California Occupational Safety and Health Standards Board listened to their pleas for more than five hours.

“If you guys don’t want us here, we can take our business outside of California,” an actress wearing a form-fitting beige dress, told the board, echoing a common threat in the long-running dispute over condoms that the lucrative business will decamp for Nevada and elsewhere if this state cracks down.

After she finished her comments, she sashayed past the board in stiletto heels. The hearing ended with the board deciding to vote down the proposal as written, but to reconsider a revised version over the next year.

There were three votes in favor of the more stringent guidelines and two votes against them; the panel, which was down two members, requires four votes in favor to pass a measure. One board member said he wanted to see “more flexibility” in the regulations, and others sought clarifications on whether spouses filming together would need to wear condoms.

Pornographic film actors, producers and directors at the Feb 18’s meeting argued that voluntary regulations adopted by the industry that require regular testing for sexually transmitted diseases were adequate to protect actors.

“This is a malicious persecution of this industry,” said a performer for more than two decades. “Other industries go unchecked with the same risk factors and the same contaminants.” Dressed in a three-piece suit, he held up photographs of bloodied mixed martial art fighters and plumbers, two occupations in which he said there could be continual exposure to dangerous bacteria. The proposed rules, he said, were “not only impossible to implement, they are impossible to enforce.”

In the prosaic language of a workplace safety, the new standards, which run 21 pages, call for a host of protections ranging from the use of condoms (which the regulations describe as “personal protective equipment”) to ensuring that “contaminated laundry is handled as little as possible, and is bagged at the site of usage.”

Sex toys and “other objects” must be cleaned and disinfected and “eye protection” must be used if there is a risk that bodily fluids reach the face.

The regulations mandate that “soaps and other cleaners are not irritating” and that “nonlatex condoms, shall be readily accessible to those employees who are allergic to the equipment normally provided.”

The case stems from a petition filed in 2009 by a charitable organization, the AIDS Healthcare Foundation, which called for greater protections for the industry. Members of the organization attended Feb 18’s meeting but were far outnumbered by the actors.

A public health consultant with the foundation, said he was disappointed with the decision. “I think it’s a sad day for public health,” he said. “Every major medical and public health organization has stated that condoms should be required on all adult film sets.” He said the campaign for greater regulation of the pornographic film industry was far from over. In addition to the proposal for workplace regulations that will be reviewed over the next year, voters in November will vote on a separate piece of legislation, the California Safer Sex in the Adult Film Industry Act.

Federal and California law mandate that employees be protected from potentially infectious bodily fluids.

California regulators argue that these laws require the use of condoms and other protection and that the proposed regulations clarify those rules for employees in the pornographic film industry.

“You are already required to wear condoms; you’re just not doing it,” the chairman of the work safety board, said. “That’s the law. It’s just not being enforced.”

The actors argued that wearing goggles or other types of face protection would make their films unsellable. They also said the regulations would force their business underground, where fewer regulations would be observed.

That point seemed to resonate with at least two of the five board members present.

“I’m actually more torn over this than I can ever explain,” said a board member. “I see what I do as my art,” said an actress who took the podium. “And in the past, throughout history, art has been persecuted.”

The actors were expansive on their love for their profession, and some were almost in tears. Some made the point that the loss of the adult film industry to places like Las Vegas, where some production has already moved, would drain California of tax revenue.

“Porn is a billion-dollar industry,” said Savannah Fox, who wore a black jacket and orange-tinted hair. “It’s not going to stop.”