WITH U.S. TROOPS, SAUDI ARABIA, OCT. 29 -- The U.S. military's top expert on the medical effects of chemical warfare said today that history shows more than 95 percent of those hit by nerve and mustard gas have survived.

"I think the threat of chemical warfare is very real. . . . But you're not talking about some devastatingly effective weapon," said Col. Michael Dunn, commander of the U.S. Army Medical Research Institute of Chemical Defense.

His message to 95 doctors, nurses and medics finishing a three-day course on treating victims of chemical attacks was simple: "There are very effective things you can do to deal with chemical casualties."

For the 350,000-strong multinational force gathered in the Persian Gulf region following the Iraqi invasion of Kuwait, the biggest fear is the possibility that President Saddam Hussein will use chemical weapons if war breaks out.

"We hope it doesn't happen, but if it does, we'll be ready," said Spec. 4 Robert Staklinski, 22, of Darlington, S.C., a medical corpsman. He had just played the victim of a simulated chemical attack, twitching and moaning on a stretcher as half-dozen doctors and medics hovered over him with a five-minute deadline to make a diagnosis and initiate treatment.

Dr. Mark Lawson, 36, a Navy gastroenterologist from St. Petersburg, Fla., said he knew "next to nothing" about chemical-warfare victims when he came to the gulf but now feels confident he can treat them and protect himself: "This {course} has taken away a lot of the fear of the unknown."

Dunn, the senior U.S. member of a NATO panel on medical-chemical defense, said his greatest concern is for troops within 25 miles of the front who are in range of Iraqi artillery and short-range rockets used in the past to launch chemical weapons.

During the eight-year Persian Gulf war, when Iraq used chemical weapons against Iran, more than 45,000 people were attacked by mustard gas, he said. Only about 3 percent died, mainly from obstruction of the respiratory system.

To a lesser degree, the Iraqis also used nerve agents, mainly Tabun and Sarin, with about a 1-in-20 fatality rate.

"Ever since World War I, right up until the end of {the Iran-Iraq war} in 1988, chemical-warfare agents which have a reputation of being lethal are really a greater cause of nonfatal injuries than they are of fatal injuries," Dunn, of Clarksville, Md., said.

"Over 95 percent of chemical casualties are living chemical casualties who aren't going to die but who stand a chance of being disabled or having a prolonged recovery," he said.

Chemical weapons were last used against American soldiers in World War I. The Iraqis, along with the Iranians, have provided the Americans with much of their insight into the modern treatment of chemical warfare victims.

Last December, Dunn said, he attended an international conference in Kuwait City and discussed chemical-casualty care with Iranian and Iraqi doctors. "There was a very free exchange of information, so there are no secrets," he said.

The Iraqis were most effective using chemical weapons against civilians and the Iranian Revolutionary Guards whose beards, worn for religious reasons, prevented a tight seal on their gas masks, he said.