Fire Chief Theodore R. Coleman said yesterday that ambulance crews learn the geography of the District by taking a two-hour orientation course and also gain expertise by "being out on the streets quite a bit."

Coleman's remarks, which came less than two weeks after a Northeast man died when ambulance drivers got lost for nearly 40 minutes, prompted an angry response from council member Jim Nathanson (D-Ward 3) during a hearing of the council's Judiciary Committee. Nathanson called Coleman's statement "unbelievable," and began a caustic debate with the fire chief about the city's troubled ambulance service.

"I'm shocked by some of the things I've heard here today," Nathanson told Coleman. "This is a city service that's a life-and-death service, and you're telling me that the guys get only two hours of training in the geography of the city? I'm dumbfounded."

Coleman said the ambulance service has "made some mistakes," but often reacted defiantly to negative comments during the two-hour hearing.

Following Nathanson's criticism, Coleman said ambulance crews also participate in daily fire house drills to familiarize themselves with city streets, and told Nathanson that few of the 143,000 calls for ambulance assistance in the city last year resulted in problems.

Nathanson responded that, considering their training, ambulance workers must be "superhuman."

Nathanson also said that last spring he rode for six hours as an observer in an ambulance that became lost on its way to the Kennedy Center.

"I've never told that to anyone before," Nathanson told Coleman as the council chambers became silent, "And I've often wondered if I should have yelled and screamed and told them they were going the wrong way. But at first I thought they were taking a shortcut."

Later yesterday, Nathanson sent a letter to Mayor Marion Barry asking that Barry remove the ambulance service from the fire department's supervision and place it under the jurisdiction of the city's public health commissioner.

Council member Wilhelmina J. Rolark (D-Ward 8), Judiciary Committee chairwoman, called the hearing to examine recent complaints against the ambulance service, which has been beset by complaints of lost and late ambulances and poor emergency dispatching.

Since 1986, nine persons have died after ambulances were slow to reach them, though no official link has been made between the deaths and delays. On Jan. 17, a Northeast man died at D.C. General Hospital after an ambulance took 40 minutes to reach the man's home. Fire officials said the next day that the ambulance had been lost.

Coleman, who has been criticized by some council members and the District's medical community, appeared before the council committee with each of his deputy chiefs, including ambulance director John M. Cavenagh. Cavenagh, the ninth person to serve as ambulance director since Coleman became fire chief in 1982, took over the position last fall.

Coleman told the committee that the ambulance service had made "great strides" recently. He said the service had lowered its average response time to 6.8 minutes, dramatically increased the cardiopulmonary resuscitation skills of city firefighters and is completing plans to buy a multimillion-dollar, state-of-the-art computer system to aid 911 dispatchers.

Rolark said Coleman was doing an "outstanding job" and called the city ambulance service one of the best in the country. Still, other council members aggressively questioned Coleman about ambulance shortcomings, specifically the division's lack of medical supervision.

Council Chairman David A. Clarke praised Coleman for not blaming a lack of money for ambulance service deficiencies, but then repeatedly asked whether poor management was behind persistent problems. Coleman disputed that, and said that no "quick-fix solutions" can repair the system.

Clarke also asked why no medical director for the service has been hired, despite a nationwide search that has lasted for more than a year. Coleman told Clarke that "we just don't seem to get many takers."

After the hearing, Cavenagh conducted his first news conference since becoming ambulance director. He said ambulance service improvements were occurring "more slowly than I would like," but said no rift exists between Coleman and him. At the hearing, Coleman said recent reports that he has not cooperated with Cavenagh are false.

Cavenagh said that since his arrival the service has rewritten its operating manual and stepped up its search for additional paramedics and a medical director who would monitor the medical services the crews provide. He said his chief goal is to make each of the city's 21 ambulances advanced life-support units; only five are now.

Cavenagh said D.C. ambulances' response times rate favorably with those of other cities with similar populations. He called reports of lost and late ambulances "isolated incidents," but said a navigating dispatcher will be placed in the fire department's communications office to assist ambulances on the way to a call.