Bacteria give carpet a nasty smell.

Imagine buying new carpeting only to find that it smells like cat urine. This happens far more often than carpet manufacturers would like to admit. "It's a problem they're very aware of," says James L. Joyce of Calgon Corp. in Pittsburgh.

In fact, some of those carpet makers asked Joyce and his Calgon colleague Jodi L. Martin to ascertain the cause of the unpleasant odor. One hypothesis held that chemicals used in making carpeting created the smell, while another suggested that microbes contaminating the carpet were the culprits. The composition of carpet backing provides an ideal environment for bacteria, Joyce and Martin note.

The investigators procured samples of new carpeting plagued by the cat-urine aroma, as well as samples judged odorfree. When they analyzed the carpeting for microbial contamination, they found that almost all the smelly samples contained bacteria that make a compound called butyric acid. While people perceive this acid in different ways, many report it has a smell similar to urine, says Joyce. He and Martin plan to more fully characterize the odor-causing germs and develop countermeasures. Their company already sells some bacteria-killing agents to the carpet industry.