In 1982, when environmentalists were campaigning to save the ozone layer, a federally funded study found replacements for only a third of the chemicals thought to cause the damage.

A ban on those widely used chemicals looked "economically ruinous," recalled David Doniger of the Natural Resources Defense Council.

What a difference a decade makes.

Industries are rushing to beat deadlines to eliminate chlorofluorocarbons. They're finding replacements for CFCs and, in some cases, making money from them.

The battle against ozone depletion offers hopeful lessons, as the Earth Summit continues in Rio. Doniger, for one, sees it as an example for dealing with `greenhouse' gases, one of the most divisive issues on the Earth Summit agenda.

World and national deadlines prodded business into action against CFCs. The Montreal Protocol bans the worldwide production of most CFCs by the year 2000. The United States recently set 1995 for the end of domestic CFC production.

"There is going to be increased pressure on everybody" to replace CFCs quickly, said Alex Sapre, Hughes Aircraft's corporate-technology manager.

To be sure, there are still some significant roadblocks: The Pentagon requires the use of CFCs in manufacturing key military components such as circuit boards. Five months after Hughes announced a CFC-free method of soldering circuit boards, the military has yet to give it blanket approval.

Medical-technology companies need the Food and Drug Administration's approval before adopting CFC-free manufacturing methods. Such approval comes slowly.

Baxter Healthcare Corp. in Irvine, Calif., recently spent six months winning FDA approval for a new sterilizing method.

There aren't yet widely accepted replacements for some CFC uses, such as the propellants in metered-dose inhalers for asthma patients and the halon gas used to suppress fires in computer rooms.

Despite these obstacles, Doniger said the transition to a CFC- free world will be relatively painless.

Look at the electronics industry, he said. Five years ago, the industry was panicking over the impending CFC ban, unsure where to turn. Now, he said, "The industry is awash in replacements."

Some of these replacements promise to save money. Hughes expects its new soldering method - which a Hughes scientist invented in his garage - to cost less than the old method using CFCs, Sapre said. Other companies that once used CFCs for cleaning have found that soap and water work just as well.

But cheap fixes are "more the exception than the rule," said Steve Risotto of the Halogenated Solvents Industry Alliance, a trade group for CFC users. More often, he said, companies have to make substantial capital investments.

That was the case with Baxter's Bentley Laboratories division. The flight from CFCs pushed Baxter's sterilization facilities from Irvine to Puerto Rico.

Baxter formerly sterilized medical devices in a gaseous solution of Freon 12 and ethylene oxide, said Bob Seguy, Baxter's environmental-health-and-safety director. Freon, a CFC, kept ethylene oxide, a sterilizing agent, from exploding. Baxter eliminated Freon by using new sterilization equipment designed to prevent explosions.

Each time Baxter switched a product to CFC-free sterilizers, the Food and Drug Administration had to review it. The last review took six months.

Military contractors have run into similar delays. The Pentagon tries to ensure the quality of computers, jet fighters and myriad other products by telling contractors exactly how to make them. In many instances, these military specifications require the use of CFCs.

The Navy has approved Hughes' new soldering method for selected projects. But Hughes is determined to win militarywide approval. It would cost too much, Sapre said, to seek approval on a project-by-project basis.

For many businesses, however, the big challenge in replacing CFCs is not finding the money or getting government approval: It's finding a replacement that works.

"There may be a few very specialized uses that are very tough nuts to crack," Doniger said.

Baxter uses CFCs to coat catheters with a protein that reduces the destruction of red blood cells during and after surgery. All the potential replacements for CFCs that Baxter has tested, so far, are toxic.

Thousands of companies nationwide are waiting for a replacement for halon gas, which is used as a fire-suppressant in confined spaces such as computer rooms, aircraft, submarines and in the bitter cold of Alaska's North Slope.

Just give researchers time, said Tom Cortina, executive director of the Halon Alternatives Research Corp., a group funded by major users of halon.

"There will be replacements," he said. "I'm fairly confident of that."