At age 35, Fairfax County Fire Department Sgt. John Hart appears the picture of health: A scuba diver and a jogger who runs two miles a day, he has been a member of the department for 13 years and a paramedic for eight years.

It is a $30,000-a-year job that Hart loves, but one that he may not have for long.

The Chantilly resident, who has answered hundreds of emergency alarms in his career, may be forced to retire on about $8,000 a year. The reason: He is a diabetic.

Over his objections and those of his doctors, Fairfax officials have declared Hart unfit as a paramedic.

" . . . You are no longer qualified for full and unrestricted duty as an emergency medical technician for reasons of safety to the public, your fellow workers and yourself," Hart was told in a letter from the department.

"It seems like I'm being punished for something I didn't do, or something I am not," said Hart. "I am not a brittle [unstable] diabetic."

Several medical experts agree, saying there is no reason that Hart, one of an estimated 1 million Americans who suffer from insulin-dependent diabetes, should be taken off his job.

"There is no evidence that he has brittle diabetes," Dr. James Moss, a clinical professor of medicine at Georgetown University, said in a recent letter. "He is physically fit to work as a paramedic."

"I can't think of a much better job for this fellow to have, to tell you the truth," agreed Dr. John Colwell, vice president of the American Diabetes Association, director of endocrinology and metabolism of the Medical University of South Carolina and professor of medicine there.

Fairfax allows diabetics whose condition is considered stable to hold numerous jobs in the county, including emergency squad service. Virginia allows diabetics to be school bus drivers, provided their condition is considered controllable.

Diabetics are prohibited from obtaining pilots' licenses and from obtaining the credentials necessary to become interstate truckers, according to the American Diabetes Association. They are not allowed into the armed forces.

Hart discovered in January 1982 that he had insulin-dependent diabetes mellitus, a condition controllable with medication.

"I know I can do the job," he said. "There's no doubt in my mind."

County officials have declined to discuss the case, saying it is a personnel matter and considered private under Virginia law.

Eric Lamar, president of the Fairfax County Professional Fire Fighters, whose organization has been helping Hart, called his a "damned unfair" case and accused the county of "kicking somebody out of their job that can do their job."

"He's got nothing but stars on his record, and why the county is taking this position is frankly beyond me," said Carey Butsavage, Hart's lawyer.

Even after he was found to have diabetes, Hart continued to pass the annual physicals required of fire and rescue personnel. In 1985, however, Hart mentioned to a doctor employed by the county that he had been involved in an automobile accident, caused by drop in his blood sugar level.

It was the only time he has suffered complications from the disease, he said. He was driving his personal truck when his vision blurred and he ran off the road and into a tree.

Hart was not injured and said he didn't lose consciousness -- a statement disputed by the three-member Fairfax Medical Examination Board.

While Hart considered the accident minor, the medical board said it represented "a very significant change in his medical condition." In September 1985, the board told Fire and Rescue Chief Warren E. Isman that Hart was no longer qualified for full and unrestricted duty as a paramedic, and suggested that he be given an administrative job.

Fourteen days later, Hart received a letter from a department official, notifying him that the department concurred with the medical board's findings, and also that there were no permanent administrative fire and rescue positions available.

". . . You are strongly encouraged to apply to the Fairfax County Retirement Board for retirement," the letter read. "If you fail to do so, the Fire and Rescue Department will be forced to file for disability retirement on your behalf." Despite Hart's objections, that request was filed with a retirement board in March.

While awaiting a retirement decision, Hart was switched to a desk job, logging warehouse inventory into a computer. The most immediate consequence, he said, is that he has been unable to practice his paramedic skills, and can't be considered for promotions.

If he is not retired, he plans to reactivate a grievance filed earlier with the county's Civil Service Commission, claiming that his removal from the paramedic's job was unfair, and constituted an act of discrimination against the handicapped.