To D.C. fire officials, beards are a safety hazard -- interfering with the seal between the firefighter's skin and oxygen mask. The department wants to bar firefighters from growing any facial hair that affects the fit of the protective gear.

To firefighter Calvert Potter and others on the force, beards are an expression of their faith. Potter, who converted to Islam a decade ago, has a two-inch beard, and he refuses to clip it.

"Basically, what they are saying to me is that a Muslim can't be a fireman," said Potter, 43, who joined the department 14 years ago. "This is part of my religion."

At a hearing tomorrow, a federal judge could settle the dispute over whether the department can force firefighters to shave their beards. The issue has been mostly dormant since 2001, when the department first tried to restrict beards and hair length of firefighters.

At the time, Potter and five other firefighters contacted the American Civil Liberties Union and filed suit to halt the department from enforcing the grooming rule, saying it violated their religious rights.

U.S. District Judge James Robertson issued a temporary injunction preventing the department from enforcing the grooming policy upon those who grow their hair or beards for religious reasons. After that, attorneys for the District and the firefighters began to discuss settlement of the case.

But little progress was made. In March, ACLU lawyer Arthur Spitzer sought a permanent injunction against the department. He said he had grown frustrated by the city's failure to draft a new policy or address the issue.

Fire officials responded in late May, when Fire Chief Adrian H. Thompson issued a new order that banned facial hair. Fire officials said that beards could allow biological or chemical agents to slip into the protective masks.

The firefighters union disputes the city's concerns about proper fit. But fire officials maintained that the department was following national guidelines. "We are way behind in personal safety issues like this," said Alan Etter, a department spokesman.

When the department began enforcing the new rules last month, six firefighters came to work with facial hair. They were placed in administrative jobs or sent to the clinic if they complained about skin conditions. The department briefly shut down several ambulances and firetrucks until they found cleanshaven firefighters as replacements.

Four of the firefighters who joined in the earlier lawsuit quickly returned to the federal courthouse for another round of legal action. Robertson issued an order last month that bars the department from forcing the men to shave until after he makes a ruling.

The other firefighters who reported for work with beards last month shaved, fire officials said.

Union officials said more than 15 firefighters who felt forced to shave developed a severe form of razor burn, known as pseudofolliculitis barbae. The condition mostly affects black men and others who have curly hair, the union said.

Firefighter Garry Mayo and others with the condition want the department to grant them waivers from the new no-beard policy. Mayo said he even passed a recent "fit" test, which measures the seal of a mask, when he had some facial hair. He said the results prove he can have a beard and not endanger himself or others during a crisis.

"This really burns and hurts," Mayo said, touching dozens of little bumps on his face. "With these bumps, I won't be able to obtain a proper seal anyway."

Lt. Ray Sneed, president of the D.C. firefighters union, was one of the men who showed up to work in June with a beard. He said that the department has allowed firefighters to have beards for decades and that he doesn't understand the rush to change tradition.

"This is dividing us along racial and religious lines," Sneed said.