highs of about 68º with low humidity

We should all be so lucky! For Marilyn Monroe's famous "subway" dress—the white halter dress immOréalized in the 1955 movie "The Seven Year Itch"—it's always a beautiful day: 68 degrees with low humidity. That's no accident. The billowy dress is currently stored in a vault at the Debbie Reynolds Hollywood Motion Picture Museum in North Hollywood, Calif., which boasts the world's largest collection of Hollywood memorabilia. There, new environmental sensing technology is being used to monitor shifts in climate— humidity in particular— that could damage the $2.2 million dress.

"Excessive humidity can be a severe enemy to antique textiles," explains Todd Fisher, the museum's CEO and Reynolds' son. "While our museum environment is extremely stable, ... we don't want to take any chances and find out one day that mold has been growing on the dress. The more safeguards we have, the better."

The sensors used are HOBO data loggers, manufactured by Massachusetts-based Onset Computer Corp. The battery-powered devices, which are roughly half the size of a standard iPod, measure and record humidity levels around the clock—even during power outages. Accompanying software converts the data into time-stamped graphs that can be displayed on a PC or Mac and printed out.

"We look at the data on a weekly basis, sometimes even daily, to make sure humidity stayed below 50 percent," says Fisher. "The data also tells us what the temperature levels were during the period, which we like to keep around 68 degrees F."