The old job of custodians was tidying up. The new one is protecting against a killer through disinfection.

As the coronavirus continues to rage and businesses and workplaces weigh the risks of reopening, janitors have a warning about the current state of cleaning in the United States. Many say they have not been given enough resources to fight the pathogen, or, in a few cases, even hot water to wash their hands. They are often not told if someone has tested positive where they are working, many said in interviews, making it difficult to protect themselves and others.

Cleaners have recently fallen ill across the country, from the University of Texas at Austin, to a Fox Entertainment lot in Los Angeles, to casinos in Mississippi. Workers in office buildings and supermarkets say they lack the time and training to do the job right. And though airlines have tried to win back customers by raising sanitation standards, pilots, flight attendants and cabin cleaners report that the efforts are still inadequate, with reused rags, unwiped tray tables and bathrooms that aren’t disinfected between flights.

Interviews with dozens of workers, employers, cleaning company executives and union officials, as well as a review of records from the federal Occupational Safety and Health Administration, reveal other glaring problems. At a Miami office tower, Martha Lorena Cortez Estrada resorted to bringing in her own Clorox and making her own masks. “Our brooms were worn out; we were mopping with just water and no disinfectant,” said Ms. Cortez, 58, who makes $ 8.56 an hour.

As the country navigates whether and how to report to work, shop, eat out, travel and educate children, it is often impossible to tell how frequently or thoroughly anything is cleaned. Recommendations from the Centers for Disease Control and Prevention are general. OSHA is investigating only a small fraction of virus-related complaints, according to a spokeswoman.

“Reopenings happened across the country without much thoughtfulness for cleaning standards,” said Mary Kay Henry, president of the Service Employees International Union, which represents 375,000 of the nation’s custodians. She is advocating better standards at the state and city level and a certification system, like the letter grades displayed at restaurants. While a few states have issued requirements, Virginia passed tougher cleaning rules on Wednesday and said it would enforce them.

Meanwhile, the task of protecting the American workplace has fallen to people on one of its bottom rungs. Many of the country’s more than two million custodians do their work at night, unseen, for minimum wage. They are often treated as a labor cost to be contracted out for the lowest possible price. Cleaning company executives and union officials say that standards have fallen in recent years as businesses have cut back on janitorial services.

“For years the industry has been really working towards a minimum scope of work,” said Laurie Sewell, chief executive of Servicon, a commercial cleaning company with 1,600 workers.

Now, many businesses are caught between investing in sanitation and slashing their budgets to survive. Some that are reopening have been laying off custodians or paring back hours, the union officials and contractors said. Last week, when San Francisco passed strict new cleaning rules for offices and hotels, owners immediately called them an unfair imposition, especially given low occupancy.

But sanitation has also become a marketing tool, with catchphrases like “deep cleaning” that experts say should be subject to scrutiny. The luxurious Miami tower to which Ms. Cortez brought the bleach advertises expanded janitorial services, but that applies mostly to common areas. With the help of the service employees’ union, Ms. Cortez and colleagues petitioned their agency for better supplies and got them. After that, she said, her supervisor started treating her harshly. She said she was fired a few weeks later, after using a microwave to make popcorn she had brought. (Her agency did not respond to messages requesting comment.)

For some custodians, the pandemic has meant unexpected leverage: more day shifts, because of more frequent cleaning; raises of several dollars per hour; a sense that what they do is not unskilled labor but a critical service based on science. Several described extensive training sessions and scrupulous new practices like disinfecting every office keyboard and telephone. At some workplaces, Covid-19 cleaning has become a premium service. Sanitation measures at the new Hudson Yards complex in Manhattan — including cleaning bathrooms at least every two hours and using color-coded rags for different products — were developed with Mount Sinai Hospital.

In Florida, Disney World reopened last weekend with new protocols in place. Trash can lids are now propped open for less touching. Custodians who see guests without masks can use company-provided iPhones to quietly report them. The Disney parks, which have long prioritized cleaning, have rehired all 2,500 of their full-time janitors in Florida.

But in a sign of the clout some low-income workers now hold, their counterparts at Disneyland in California helped push back that park’s reopening, saying it was unsafe.

“It’s scary to know, as a custodian, that if we miss the slightest little thing, someone could carry this halfway across the country,” Artemis Bell, a Disneyland worker, said.

‘Quick Turns’

To protect and lure back customers, airlines have raced to adopt new cleaning methods, often emphasizing overnight disinfection. Scientists consider a different task to be paramount. “The most important thing is to clean the airplane after each use,” said Dr. Qingyan Chen, an engineering professor at Purdue University who has led infectious disease research for the Federal Aviation Administration.

Though surface transmission is not as significant a threat as face-to-face contact, according to the C.D.C., scientists say disinfection is critical for high-touch areas like doorknobs and bathrooms, where flushing toilets may spray coronavirus droplets.

But long before this crisis, many airlines outsourced their custodial jobs and minimized between-flight cleanings. The longer airplanes sit on the ground, the fewer flights made and tickets sold. So for decades, the job has usually been done by contract cleaners who dash onboard, dispose of trash, tackle obvious messes and disappear, aviation workers and union officials said.

Now, most airlines are relying on those workers to prevent contagion. Standards are higher overall, and many planes seem more sanitary, according to cabin cleaners and other personnel. Delta, for example, said it was using electrostatic sprayers — which coat surfaces with disinfectant particles — before every flight. But workers from a number of airlines said that many between-flight cleanings were rushed and inconsistent. Pilots registered the same concerns in a union report last month.

“The only part of the passenger seats that was wiped down was the seat itself,” one pilot wrote. “Not the area that passengers touch constantly, such as seatbelts, window shades, arm rest, etc. Also, the entire plane was supposedly wiped down in less than 10 minutes.” Last week, the Association of Flight Attendants began a survey to assess sanitation and other safety issues. Of the many hundreds who have responded so far, only 44 percent of flight attendants said their planes were thoroughly cleaned and disinfected between flights during the day.

Barbara Gomez, 62, works the evening shift at Los Angeles International Airport, cleaning American Airlines planes for $ 17.55 an hour. By the middle of the night, she said, things often slow down and she has more time for each cabin. But she said the first few airplanes of the evening were “quick turns,” in which she and a handful of other colleagues had under 10 minutes to clean.

“Just pick up trash, check the seatbelts, cross them, make it look good, and if a tray table looks dirty, you wipe it,” she said, adding that they often did not have time to open every one. “If it’s clean, we just keep going, because we have to get off,” said Ms. Gomez, who complained to the service employees’ union.

Two co-workers echoed those details and named other potential hazards, like beginning their cleanup before passengers disembarked, increasing the risk of close contact. Sometimes they do not have time to disinfect the bathrooms, they said.

Paper towels are always available, but before the pandemic they were given one rag per shift, which they had to sign out and return. Now they are supposed to get two, one of the co-workers said. “Some nights we’re out of rags, completely out,” Ms. Gomez said.

A spokesman for her employer, JetStream Ground Services, disputed that account, saying it had added extra staff for each cleaning and made available as many rags as necessary. But rags are not supposed to be used, let alone reused, according to a spokesman for American Airlines. He called the workers’ account a troubling violation of its new standards, which he said included between-flight disinfection of bathrooms, tray tables and seatbelt buckles, as well as other frequently touched surfaces like armrests, window shades and entertainment screens.

Without a Warning

Several contract cleaners described a Covid-19 nightmare: being expected to clean a space where someone infected may have been, and not being made aware of it.

After years of economic struggle, Steve Kelley, 54, a cleaner in Pittsburgh, cherishes his $ 18.07 office custodian job, especially now that working from home is becoming standard for so many organizations. “We work with the fear that we won’t be working,” he said.

But he recently learned through other building staff that several people where he worked had tested positive. He and co-workers demanded better notification. “They have to start telling us what, where, who,” he said.

Even when custodians have a clearer sense of the potential dangers, they can feel obligated to step into higher-risk situations. In April, Hilda Aguilar’s cleaning company assigned her to a drive-through testing site in San Clemente, Calif., that was about to open to coronavirus patients. To her surprise, they asked her to continue cleaning in the evenings even after it was operational, with only gloves and a mask and what she felt was insufficient training, she said. Ms. Aguilar — who is 39, makes $ 13.50 an hour and was a nurse in her native Mexico — refused until given a protective suit. (A representative from Performance Building Services, her employer, said that Ms. Aguilar was trained beforehand and provided with a hazmat suit, and that she was working after hours in offices used by medical staff.)

The risks cut two ways, with implications for businesses and their customers. Maria del Carmen Mendez and her husband are contract cleaners at a Cheesecake Factory in Mission Viejo, Calif., where they were not given masks and had to bring their own, she said. A few weeks after the restaurant reopened on June 11, he felt sick but continued working. Even after Mrs. Mendez, who is 31 and pregnant, told supervisors he had been hospitalized with Covid-19, they expected her to fill her shifts. “I went voluntarily,” she said. “I needed to keep working.”

A representative for the Cheesecake Factory said the company would investigate the incident, emphasizing that the cleaners worked for an outside contractor. That contractor did not respond to requests for comment.

Even some custodians with better working conditions are uneasy about their role in reopening. Elizabeth Martinez, 36, along with her mother and sister, followed her father into the business of cleaning premium New York office towers. Her father, Fortunato Martinez, had a $ 27-an-hour union job, plans to celebrate his 20th anniversary as a janitor and a special box holding every one of his pay stubs.

In March, her mother contracted the virus, and Ms. Martinez and her father fell sick, too. In April, her father died, his retirement papers already in. In May, she was called back to work.

As Ms. Martinez disinfected the same empty desks over and over, she realized that her real job was to instill confidence for white-collar workers.

“We have to take on risk so the tenants have less risk,” she said.

Disney’s Big Experiment

The Disney theme parks are now conducting an unintended experiment in whether janitorial work can be made safe for both guests and cleaners.

Disney World in Florida and Disneyland in California were both supposed to reopen their gates this month. But as cases rose in California, unions for custodians and other workers wrote to Gov. Gavin Newsom expressing reservations.

“Our work as custodians is undone as we finish it,” said Ellie Gonzalez, 26, who makes $ 15 an hour and has no health benefits as a part-time employee at Disneyland, which she called especially worrying during a pandemic. “I was thinking about how we disinfect the handrails. As soon as we disinfect it, someone else comes and touches it.”

Mr. Newsom declined to give any theme parks the green light.

The health situation in Florida may be even more severe. On Saturday, Disney World reopened. On Sunday, Florida reported 15,300 new cases, the highest single-day total of any state.

Now, the park is trying to keep the virus at bay in part through the sheer effort of its workers. “People trust Disney, and we have a big responsibility to deliver on that trust,” Josh D’Amaro, Disney’s theme park chairman, said during opening weekend.

Rides are cleaned every two hours. A special team (“the Incredi-Crew”) enforces physical distancing and mask wearing.

“I’ve been one of the harshest critics of Disney in terms of how they treated its cast members,” said Eric Clinton, the head of the custodial union, adding that workers were jittery their first week back, and that the park continues to add new rules. “I think Disney is going to get this right and get this safe.”

The coming weeks may tell whether the California or the Florida decision leaves custodians, and everyone else, better off. The West Coast janitors will go longer without paychecks, a loss somewhat offset by Disney’s benefits — a year of health care coverage for full-time workers — and the state’s relatively strong safety net. In Florida, unemployment coverage is far weaker, and even Disney workers who qualify have struggled to get access to the money, making economic stress an unseen force in the Orlando park’s reopening.

Kim Hanley, a Florida custodial coordinator who makes $ 19.25 an hour, said that during recent weeks of training, Disney’s new procedures made work a sanctuary for her. At her local grocery store, most customers have not been wearing masks, she said.

“Compared to the rest of Florida, this is safer,” she said.

Lauren Messman contributed reporting. Susan C. Beachy and Kitty Bennett contributed research.