Dupont has developed a selectively permeable membrane fabric that allows sweat evaporation and body heat to get out of moon suits emergency workers wear in areas where dangerous chemicals may be present. This keeps the people wearing the suits cooler, while still keeping out harmful chemicals or biological organisms. In addition, the new suits are up to 50 percent lighter than existing equipment and can be folded to fit in a small duffel bag. The new suits are being tested by troops and emergency personnel. Selectively permeable membranes have been available for some time, and since the 1980s have been common in sports wear and winter clothing. However, the new selectively permeable membranes are robust enough to keep out all harmful agents, while still allowing sweat and heat to escape.