By Sandy K. Johnson

In a modest ranch house on the outskirts of Austin, Texas, Shan Zhou prepares a basic stir fry recipe. She heats oil to a smoking hot temperature and then stirs in vegetables, which sear in the oil and send up a plume of steam. She pours in packaged stir fry sauce, which sizzles in the wok.

Shan wasn’t cooking lunch. She is a researcher for a sophisticated, first-of-its-kind field study of pollutants in indoor air. Behind the scenes, in four trailers bristling with state-of-the-art equipment, an army of researchers is tracking particle counts; chemical composition, including physical and chemical properties; the species of gases in the air; and a host of other scientific measurements.

Welcome to HOMEChem, which stands for House Observations of Microbial and Environmental Chemistry. Cooking exercises are replicated over and over, along with other everyday household activities like cleaning countertops and mopping floors. Cooking and cleaning, along with the interactions of personal care products, are the focus of this month-long collaboration of 15 university professors and 60 researchers. They are trying to analyze indoor pollution and how it might affect your health.

At the UTest House at the University of Texas, this team of scientists is collecting a treasure trove of data from 60-plus instruments that will be analyzed and studied in the coming months and years, according to Marina Vance, an assistant professor of engineering at the University of Colorado Boulder and co-principal investigator of HOMEChem.

Since the Clean Air Act of 1970, the outdoor environment has been studied extensively, prompting people and businesses to modify their behavior and products in order to cut down on carbon dioxide emissions. Indoor air is not regulated, however, and therefore has drawn little scientific scrutiny. But Americans spend a whopping 90 percent of their time at home or at the office and there is scant scientific research about the air they breathe indoors.

Rich Corsi, professor and Joe J. King Chair in Engineering at the University of Texas, said scientists have been studying the indoor environment for 20 years and have “barely scratched the surface.”

Why has the indoor environment been ignored during decades of focus on outdoor pollution? Regulations drive research, and most regulations are focused on the outdoors, Corsi said, and there is a sense that people’s homes are their private castles and the government shouldn’t intrude. There are also literally millions of buildings in the U.S.; each is its own micro-environment.

The university purchased UTest House in 2007 with a National Science Foundation grant. They have conducted research on emissions, pollutant transportation, how walls filter pollutants and more. But -- “never at this scale, never so deep,” said Atila Novoselac, an engineering professor who supervises the test house.

From the outside, the house looks like your basic 1,200-square-foot, three-bedroom, two-bath manufactured house. But it has three HVAC systems and miles of wires, sensors, tubes and monitors that snake around the walls and ceilings.

Largely invisible to the naked eye, gases and particles abound in the indoor spaces, often mutating as they react with each other and with human skin and breath. “Particles oftentimes carry chemicals with them that you don’t want persisting in your lungs because they can get into your bloodstream,” Corsi said.

Each researcher is tasked with tracking a specific item on the extensive HOMEChem checklist. The terabytes of data will eventually lead to scientific papers that will help better inform the public about indoor environments. Behaviors may be modified, product development may change and health issues may be identified.

Paula Olsiewski is director of the Chemistry of Indoor Environments program at the Alfred P. Sloan Foundation, which is underwriting HOMEChem. She said the data may change how people ventilate their homes or what products they bring into their homes or how they cook. “I firmly believe people will make different choices indoors,” she said.

Because this collaborative effort is a first, she said, the results are “a big mystery.”