Trying to Make ‘Clean Rooms’ Even Cleaner : Technology: Two Southlanders have a patent on a substance that tests clean room filters without polluting.

A Pasadena chemist and inventor, A. J. Bauman, considers most “clean rooms”--surgical theaters and sealed-off manufacturing areas for pharmaceuticals, contact lenses and microchips--to be far from spotless.

In fact, he says, they are contaminated by the very substance used to test the air filters meant to keep them pure.

And he and a partner have a better idea.

The conventional test substance is known commercially as DOP--aerosol dioctylphthalate, a plastic softener that adds suppleness to everything from garden hoses to auto dashboards. The film that collects on a car’s upholstery and windshield on a hot summer day is the same material, brought to the upholstery surface by the warmth.

“It is fantastically common,” Bauman says.

Under pressure, DOP particles are also useful for testing the hundreds of thousands of super-filters used in clean rooms around the world.

Construction of clean rooms has slowed with the stalled economy. But in 1988, the most recent year for which figures are available, 388,000 new filters were installed in the United States, according to Sheila C. Peyraud, marketing manager of Donaldson Co., one of the three largest U.S. filter manufacturers.

Yet when DOP is used to test the filters, it is not systematically recovered. And air circulation in clean rooms is so tightly controlled that Bauman compares them to “a goldfish bowl where the water doesn’t get changed very much.”

Sooner or later, Bauman says, the walls, ceilings and equipment of clean rooms are covered with a minuscule sheen of DOP.

Unfortunately from a health standpoint, many scientists suspect that DOP is a slow-working carcinogen, possibly linked to increased incidences of liver cancer after years to decades of exposure.

For their part, microchip manufacturers worry about any pollutant that could ruin a chip’s electrical conductivity.

“It’s the No. 1 concern in our industry to remove any contamination in the clean room,” says Eric Winkler of Semiconductor Equipment Manufacturers International. “You can lose millions if a large fabrication line goes down.”

Winkler estimates that the almost 800 fabricating lines worldwide each use 500 to 1,000 of the super-filters.

Authorities, including the U.S. Army surgeon general, the National Cancer Institute and the U.S. Consumer Product Safety Commission have listed DOP at one time or another as a weak potential carcinogen in humans. It is more widely agreed to that it causes cancer in rats and mice.

The safety commission, after a 1985 study, recommended severely restricted use of DOP in such items as polyvinyl baby teething rings.

Yet other researchers are not persuaded. And even if DOP does increase the statistical risk of getting cancer, there are many weak carcinogens in daily life. Thus, there has been little enthusiasm for wider limits on this one.

Bauman and his company, Thermofoam Inc., have more than a passing interest.

A chemist who spent 16 years studying moon rocks and rocket fuels at Caltech’s Jet Propulsion Laboratory , Bauman owns the patent--along with co-inventor Frank A. Morelli of Claremont-based Monitronics Inc.--for a DOP substitute. Their test material is an extremely fine silica particle, suspended in a liquid, with a chemical coating that Bauman says makes it harmless to humans.

Yet eight years and numerous trade shows after Bauman and Morelli secured a patent, sales have grown slowly--”a couple of thousand dollars” a year, according to Morelli.

Largely to blame have been initial problems with the testing machines used to blow the silicon against the filters. “If you didn’t know what you were doing, it was like filling a coffee cup with a fire hose,” said a contractor who used the first testing devices. Used in such large amounts, the silicon was also expensive.

“It’s a good solid aerosol,” said John Ortiz, air-cleaning and testing specialist at Los Alamos National Laboratories in New Mexico, who evaluated the product several years ago. “It just had problems with agglomeration--particles attaching to each other. And that makes the size bigger than you really wanted.”

Ortiz was also concerned that the silicon could pile up on the filter and lower the amount of air getting through.

But Bauman and his supporters say these technical difficulties have been solved.

“If you generate it in a rational way, it’s no more expensive” than DOP, says Roy Zeagler, president of Air Filtration Engineering Co. of Tucson, Ariz., which conducts clean-room tests on contract for labs and other specialty companies.

DOP manufacturers maintain that their product is safe.

Eastman Chemical Products Inc., a subsidiary of Eastman Kodak Inc. and a major producer of DOP, began fresh research late in 1990 to prove that in reasonable concentrations, DOP doesn’t cause cancer.

“I don’t think there’s any question that if you feed high doses to rats and mice, you’re going to get liver tumors,” says W. Mills Dyer Jr., technical fellow at Eastman Chemical, referring to experiments done by the National Cancer Institute in the late 1970s. “We are seeing if we can’t more clearly demonstrate that it would be very unlikely at any reasonable exposure levels to be a carcinogen to people.”

Bauman’s campaign, though, may be about to get a boost from an unexpected source--the increasingly miniaturized computer chip.

Smaller and smaller chips are being produced in cleaner and cleaner rooms. Recently, IBM announced that it can pick up and deposit single atoms of the silicon used in microchips.

Clean rooms have long been defined by engineers as having no particles larger than 0.3 microns--the average size of tobacco smoke or smog particles or a bacterium. But Bauman and Morelli’s silica is only 0.2 microns--already the standard measure for most state-of-the-art clean rooms, particularly in manufacturing.

Intel Corp., the world’s largest microprocessor manufacturer, uses the silicon in all its new clean rooms.

“There is a fair amount of art to the manufacturing process,” says Terry McManus, corporate manager of environmental health and safety at Intel. “People are concerned about bringing anything foreign into the system anywhere.”

Meanwhile, Bauman and Morelli continue to market their product, Dri-Test, on a broader scale to medical facilities and conventional labs. Clients so far include the Lawrence Livermore National Laboratory, International Business Machines Corp., the Kenneth Norris Jr. Cancer Hospital and Research Institute at L.A. County/USC Medical Center and other facilities where DOP-free clean rooms are required for some specialized needs.

“The basis of all this technology is the filters,” Bauman says. “They’re the only thing between the clean rooms and the outdoors.”