Twenty-seven commercially available rigid foam materials were tested to delineate those most suitable for use as a sealant in underground mine stoppings. The rigid foam industry was surveyed for possible candidates based on published properties, cost, and application equipment. Using a process that recognized those properties of rigid foams that were important for use as mine stopping materials, laboratory tests reduced the initial listing to two. Flammabiltiy, air permeability, and mode of application comparisons played major roles in the selection process, with adhesion and cost comparisons being minor factors. Standard ASTM tests were employed where applicable. In-mine tests were conducted on the final two candidates, using them as the main air barrier and as a joint and perimeter sealant for ventilation stoppings in a nonmetal mine.