Many scientists believe that indoor pollutants have contributed to the symptoms of illness as much as the carpets.

Some ventilation is essential of course - to remove indoor atmospheric pollutants - particularly from gas appliances.

HRVs also can improve air quality in homes that have other indoor pollutants.

CO is considered to be a surrogate for human bio-effluents and may correlate with other indoor pollutants.

Both indoor and outdoor pollutants, like pesticides and auto emissions, are among the chief suspects, she said.

Some say the problem is not with carpets alone but with other indoor pollutants.

"It adjusts to most windows and allows fresh air in, helps escort indoor pollutants out."

Renewable energy can contribute to improved this situation by avoiding exposure to indoor pollutants.

Its chief source was cigarette smoke, the greatest source of indoor pollutants.

Researchers are now focusing on indoor pollutants and allergens that may have been introduced as part of modern housing.