As more than 100 hospital workers remain in self-imposed quarantine in California, a proposed regulation designed to protect them from infectious diseases such as the coronavirus languishes inside a federal agency.

The draft regulation would require employers to provide protective gear for health-care workers and to create infection-control plans, which could include building isolation rooms. The Obama administration was working to adopt the regulation, but the Trump administration in 2017 moved it to a less urgent, long-term agenda and work on it stopped.

Now, members of Congress, unions representing health-care workers, and the former head of the Occupational Safety and Health Administration (OSHA) are calling for the proposal to be expedited. They are petitioning the Labor Department, which oversees OSHA, to turn to a little-used federal law that allows the agency to issue a temporary emergency standard when a “grave danger” or “new hazards” emerge in the workplace.

Several unions are asking that any emergency regulation also include people working for airlines, mass transit systems, prisons or in other workplaces where laborers may be exposed to the coronavirus.

In a letter sent Thursday afternoon to Labor Secretary Eugene Scalia, Reps. Robert C. “Bobby” Scott (D-Va.) and Alma Adams (D-N.C.) said the “widespread epidemic of a virulent novel airborne” make it “clear it is time” to set an emergency standard.

“OSHA is the only agency in the federal government authorized to enforce safe working conditions for the nation’s workers — including those in health care facilities,” wrote Adams and Scott, who is chairman of the House Committee on Education and Labor. “As we enter into what is likely to be the greatest infectious disease crisis this country has faced in over a century, it is in the national interest that OSHA be on the forefront of protecting workers essential to the country’s health care system.”

The former head of OSHA under President Barack Obama said years of work have gone into the draft regulation, which included seeking and including advice from the health-care industry. That could allow OSHA to move quickly.

“The framework is there. If OSHA wanted to modify the standard, it could put it out tomorrow,” said David Michaels, who now works as an environmental and occupational health professor at George Washington University.

OSHA and Labor Department officials did not respond to a request for comment. The White House coronavirus task force also did not respond to requests for comment.

Jane Thomason, with National Nurses United, said nurses and other health-care workers are dealing with unclear and sometimes haphazard safety protocols that can leave them unprotected.

For example, at the UC Davis Medical Center, a patient infected with the coronavirus was not tested until four days after the patient was admitted. Because of the delay, more than 100 health-care workers, including about 30 nurses, quarantined themselves in their homes on Saturday after they were exposed to the patient. They remain in their homes.

“What happened at UC Davis underlines the need for health-care facilities across the country to implement the highest level of protection that nurses and health-care workers need,” said Thomason. “When nurses and health-care workers have those protections, that means patients and our communities are also protected.”

Thomason’s group filed a petition with OSHA on Wednesday, calling on it to issue a temporary emergency standard for the coronavirus.

She said a national survey of 6,500 members, which the union released Thursday, shows why it believes a standard is needed.

In it, 58 percent of nurses said their employers had instituted screening procedures for patients with fever or respiratory symptoms. Also, 44 percent of nurses said their employer has provided them with information about the virus.

“That’s less than half of nurses — that’s kind of terrifying,” Thomason said.

On Friday, the AFL-CIO and a half-dozen other unions plan to join with Scott and others in calling for an emergency standard. The petition identifies 14 public and private “high-risk” industries — including firefighters and cruise ship workers — and asks that the standard apply to all 42 million workers employed by those industries.

The unions said that although guidelines have been issued by the U.S. Centers for Disease Control and Prevention in response to the coronavirus, it is not mandatory for any workplace to follow them.

“Preparing for and protecting health care workers, emergency responders, and transportation workers at risk of exposure to coronavirus must be mandatory,” the petition says. “Only an emergency temporary standard can quickly accomplish this objective.”

If OSHA adopted a temporary standard, it would be in effect for six months, at which time the agency would be required to adopt a final version if it wanted the standard to stay in place.

A temporary or permanent standard would require organizations that employ health-care workers — and perhaps others that might get infected on the job — to develop a plan for their facilities that would protect workers from coming in contact with the virus.

The infection-control plans would include creating a protocol for when a patient arrives with symptoms of a respiratory illness and an assessment of whether appropriate protection gear — as well as a sufficient amount of it — is available.

The plans would also prescribe a training program for employees.

“The plan should be kept up to date with CDC guidance,” said Michaels. “It shouldn’t be static.”

OSHA rarely makes use of the emergency law, and courts have frequently vacated temporary emergency standards when they were challenged by industry. The OSHA website indicates that no emergency standards have been issued in decades.

Julie Tate contributed to this article.