The agency that hears federal workplace appeals anticipates a wave of challenges to furloughs, but several attorneys who practice federal employment law say workers considering filing such a complaint should prepare to face long odds.

More than 1 million federal employees could be notified as soon as Friday that they face unpaid time off due to sequestration. The number of furlough days would vary among agencies, as would the timing — although due to a 30-day advance notice requirement, furloughs couldn’t begin until early April.

Employees are entitled to respond to such a notice, review agency documentation and receive an agency reply. In addition, for up to 30 days after their first actual unpaid leave day, employees may file an appeal with the Merit Systems Protection Board, a quasi-judicial agency with regional hearing officials and a three-member appeals board.

MSPB Chairman Susan Tsui Grundmann sent a letter to Congress last week warning about the potential impact.

“It actually hits us three times,” Grundmann said in an interview. “First, there’s going to be an impact on the workload. Second, we might have to furlough our own employees. Third, if our own employees choose to appeal their furloughs, those appeals could not be heard here. We would have to pay for that to be heard outside. It’s really the perfect storm for us.”

During fiscal 2012, MSPB issued about 7,600 decisions. If more than 1 million employees are furloughed and just 1 percent of them file appeals, “that would be about double what we usually process,” she said.

“We still are going to be hearing cases on veterans’ claims, we’re still going to be hearing whistleblower cases, appeals of retirement decisions,” she added.

Grundmann noted that it took MSPB several years to process its last large surge of cases, about 12,000 appeals of air traffic controllers fired for striking in 1981. Even if Congress were to provide money to hire more hearing officers, as happened at that time, the agency would be facing a major challenge because of the time it would take to train them, she said.

However, employees who file such appeals will find that their rights are limited, said several attorneys who practice in that field. Filing an appeal would not prevent an employee from being furloughed, for example — those who later prevail merely would receive back pay, attorney’s fees and, in some cases, compensatory damages.

“In most cases, I’d think employees would have these decisions sustained by MSPB in the absence of unusual circumstances that the employee could show,” said William L. Bransford of Shaw Bransford & Roth P.C. “MSPB would uphold the furlough unless the employee could prove what’s called an affirmative defense.”

Such grounds could include allegations such as favoritism, discrimination or whistleblower retaliation.

“If an employee could prove those things, they could win an appeal,” Bransford said. “But the burden of proof is on the employee. You have to show you’re being treated differently than other employees. If everyone is being treated the same, you’re not going to be able to show that.”

“If they furlough the whole office, how are you going to claim disparate treatment?” asked Edward H. Passman of Passman & Kaplan P.C. “The ultimate determination of whether there’s furlough is at management’s discretion. All they have to prove is the efficiency of the service, which is a fairly easy burden for an agency to meet.”

In terms of precedent, furlough cases are “largely unexplored territory,” said Jessica Parks, a former vice chair of MSPB, now of Kator, Parks & Weiser, P.L.L.C. She said that many of the prior cases involved special rules applying to one small group of employees, administrative law judges.

In one leading case from 1984 not involving such employees, MSPB upheld a furlough after ruling it to be “a reasonable management solution to the financial restrictions” on the agency. MSBP said it would not interfere with management’s decision without a showing of “disparate treatment among similarly situated” employees.

“It comes down to are there going to be fairness issues, and that depends on how each agency handles it,” Parks said.

In addition to unequal treatment, an employee could allege an error in the required procedures. “While that may sound simple, we see in our practice that agencies often don’t follow procedures correctly,” said Parks. “Sometimes they make mistakes. If that happened in a particular case, it could result in the reversal of an action and then back pay and other relief.”

Said Bransford, “This really is kind of an unprecedented time and we don’t know whether federal employees are going to react by filing a lot of appeals or whether they’re going to feel it’s not worth their time and effort. Not that they can’t win, but it’s a real uphill battle.”