Wearing a vest can actually keep a construction worker cooler on a hot day, thanks to a heat transfer system developed by Electric Fan Engineering. The Thermal Star cooling vest uses a battery-powered fan to circulate air through a cooling material that absorbs perspiration. On a hot day, the forced air moving through the vest provides thermal conductivity. Fix-mounted systems are available for both 12- and 24-volt applications. Also available is an optional portable system with a rechargeable battery pack.