Chemicals in synthetic carpeting can react with a component of smog to generate unpleasant aromas. The resulting scents, which may persist for up to 3 years, are independent of the months-long release of chemicals that's come to be known as new-carpet smell.
To investigate a potential contributor to sick-building syndrome, environmental engineers at the University of California, Berkeley exposed squares of nylon or olefin carpeting to airborne ozone at a concentration of 100 parts per billion (ppb). Though high, that's not beyond what's present in some large cities. After 7 to 10 days, the researchers measured gases coming off the samples–which were either intact or with most of their upper pile sheared off so the team could check the effects of the backing. The researchers then extrapolated the results to what might occur under prolonged exposure to the lower ozone concentrations typical of many urban homes and offices.