AT FIRST, of course, they thought it was just some kind of flu going around. But then the workers in the San Diego high-rise building noticed that they felt better whenever they were away from the office and sick again once they returned.

They thought of all those Legionnaires in Philadelphia, the ones who got so sick they even had a bacterium named after them. Legionnaires' disease had been caused by germs spread by a hotel air conditioning system. Maybe, the office workers thought, their illness was linked somehow to their office building. But why were the headaches and wheezing only confined to the 10th floor?It was time to call in Gray Robertson.

Robertson, president of Healthy Buildings International in Fairfax, Va., specializes in diagnosing and treating sick buildings in the United States and abroad - to date a total of about 40 million square feet.

Robertson inspected the San Diego high-rise building and figured out the problem. A law firm had moved in on the 10th floor. The law partners wanted to be certain that nobody could overhear the conversations they conducted in their offices, so when they had partitions constructed they made sure the wallboard went all the way up to the concrete slab in the ceiling.

The trouble was that in eliminating eavesdropping they also eliminated a passageway for stale air to get out and fresh air to get back in.

With only recycled air, eventually there was a toxic buildup of chemicals: pesticides, disinfectants, detergents, copy machine fluids, carbon monoxide, adhesives, formaldehyde. The residues of modern life. It was inevitable, says Robertson, that people would get sick.

Every year, hundreds of thousands of people suffer from sick-building syndrome or from building-related illnesses, says Robertson, who visited Salt Lake City to campaign for cleaner indoor air. He estimates that as many as half of all large buildings in the United States are sick to some degree.

Sick-building syndrome surfaced in the 1970s, when two trends converged. Natural materials like wood and cotton gave way to plastics and acrylics. (By now, according to the Environmental Protection Agency, there are up to 500 organic chemicals in modern buildings, some of them in concentrations 100 times greater than normal.)

At the same time, to cut down on energy costs, architects began designing buildings that would be cheaper to operate - the ceilings were built lower, the walls more air-tight, the windows sealed shut. And building engineers began cutting corners, too, shutting off fresh-air intake dampers, buying less-effective air filters, not cleaning out the air-conditioning ductwork.

"So many times," says Robertson, whose clients have included hospitals, schools, government agencies and large corporations, "we've gone into buildings and found absolute stupidity and carelessness."

In some cases, the air intake comes through the garage, so that fumes from cars and trucks get sucked up into the building. Or sometimes it's located next to the building's exhaust, or next to the cooling tower, where bacteria and fungi find a friendly home.

The National Institute for Occupational Safety and Health inspected nearly 450 buildings and discovered, says Robertson, that in 62 percent there was insufficient fresh-air intake. Half of those buildings, in fact, were running on 100 percent recycled air.

"I've made a challenge to any (building) engineer anywhere," says Robertson. "Operate your building at maximum ventilation rates for a month. Then operate it at minimum rates for the second month. Then take the savings and divide them by the number of people in the buildings.

"You won't save more than $50 a year per person," he insists. On the other hand, illness and absenteeism can cost thousands of dollars a year. "We're being penny-wise and pound-foolish." The problem, of course, is that the people who manage buildings are not the same people who pay for sick employees.

Robertson points to a study done by the Walter Reed Army Institute of Research. The institute studied 400,000 Army personnel, half of whom lived in old, drafty buildings and half in modern buildings. After studying the personnel for four years, the Army discovered that the people who lived in the new buildings had 50 percent more sickness and absenteeism.

When it's called in to diagnose a sick building, Healthy Buildings International uses fiber optics and other high-tech sleuthing methods. Often HBI finds that the building's air-conditioning ductwork contains potentially allergenic fungi or bacteria, including streptococcus and Legionella pneumophila. Air-conditioning ductwork, notes Robertson, is a perfect breeding ground for germs - dark, enclosed, humid, climate-controlled and dirty.

Just about all sick building problems can be cured, he says. Ventilation rates can be increased, ductwork cleaned out and sanitized, and filtration systems upgraded.

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Panguitch High nails culprit in mystery illness

For three years, school officials in Garfield County have been trying to solve The Mystery at Panguitch High. Now it looks like the case may soon be closed - even though there are still plenty of questions about the culprit.

After Panguitch High School was opened in 1986, students and teachers began experiencing unexplainable headaches, dizziness, fatigue and sore throats. First dismissed as the flu, the symptoms later were found to worsen during the school week and lessen over the weekend.

People began to suspect that the school building itself was the culprit, but inspections and blood tests could not pinpoint exactly what it was about the building that was the problem.

Because not everybody was sick - about one-third were affected by symptoms - some people wondered if it was just a case of hypochondria.

"The big thing was that you tended to blame it all on your mind," remembers Cindy Judd, Panguitch High PTA secretary. "But we had rashes, and that helped."

Within the past month, Cellabar and Associates in Phoenix, Ariz., inspected the building and concluded that the school's ventilation system is "out of control," says Garfield County School District Superintendent Philip Blais.

Although he is waiting for a detailed written report from Cellabar, due at the end of the week, Blais says one of the contributing factors is the school's coal-burning heating system. It is believed that fumes from the smokestack are being sucked back into the classrooms.

"We may have to redesign the whole (ventilation) system," says Blais.

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Poor ventilation may be the culprit

Gray Robertson is all for smoking bans in public places, but he worries that they may be, in effect, a smoke screen.

The real problem, he says, is not smoke but poor ventilation.

"If you want to have a smoking ban, call it that, period. But if you really want a Clean Air Act, you need minimum ventilation rates and minimum filtration standards," says Robertson, a chemist and president of Healthy Buildings International.

Now that smoking is prohibited on most domestic flights, some airlines have been cutting back on their ventilation rates, says Robertson. "They're missing the whole point." The point, he says, is that when there isn't sufficient fresh air in a building, or an airplane, people tend to get sick.

Symptoms of sick building syndrome include sore throats and eyes, fatigue, coughing, nausea, dizziness and headaches.

In addition, building-related illnesses caused by dirty air-conditioning ductwork can include strep infections, urinary tract infections, gastro-enteritis and other digestive disorders, asthma, allergies, dermatitis, Legionnaires' disease and other respiratory problems.