The meetings last longer in Andy Kaufman's office and lab on the University of Hawai'i-Manoa campus, and it isn't just because he's a likeable guy with a lot to say. People don't know why at first, but they just feel better when they are there. They breathe easier.

The reason? Kaufman's oasis of potted plants. He's put them on tables, desks, the floor, everywhere. He has 16 plants crowding his office, and almost that many around the lab. Friends call the place a jungle, but the plants are silently and steadily scrubbing the air of indoor pollution.

Rooms full of invisible toxic vapors are an ugly byproduct of modern convenience. They float off a variety of common objects: Facial tissues, drapes, carpet, pressed-wood furniture, new plastic items, furniture waxes, adhesives, disinfectants and cosmetics. Any petroleum-based product can be a culprit, said Kaufman, an associate professor and landscape specialist in the Department of Tropical Plant and Soil Sciences.

Environmental experts call this off-gassing. It creates "new car smell" or the odor that comes with a new plastic shower curtain.

The typical indoor space is said to contain growing amounts of chemicals known to cause cancer, including formaldehyde, benzene, ammonia and xylene/tolue. Indoor pollution is such a problem that the U.S. Environmental Protection Agency recently listed it as one of the top five threats to public health.

"It's quite scary when you actually think about it," Kaufman said. "They are cancer-causing. And there are other nasty things, too, that they cause."

Among those sensitive to such indoor pollution, common ailments include eye, nose and throat irritations, allergies, asthma, blurred vision, fatigue and headaches, among others.

Plants offer a good defense and a host of other health benefits, said Kaufman, who studies the ways plants affect people, sometimes attaching an array of sensors to a person in order to monitor brain waves and heart rates as they look at landscapes.

"Plants have shown to reduce stress," said Kaufman. "They increase concentration. They lower blood pressure and they totally clean the air. They take out volatile organic compounds, which are basically petroleum based."

Because they raise humidity slightly, plants relax people, he said. They also filter dust from the air.

Some of the key research was done for NASA in the 1970s and '80s, as officials pondered closed environments in space. They found that plants that clean the air emit water vapor that in turn creates a pumping action to pull contaminated air down around a plant's roots, where it is converted to food.

Basically, it's all about bringing nature's life support system indoors.

"A nice house plant with good potting media is a good bio-filter," Kaufman said. "When you go out to the mountains, people say, 'It smells so clean here.' Well, there you go."