The objectives of this research were to examine and to document the laboratory performance of several brands of rigid urethane foam. Eighteen brands, produced by thirteen manufacturers, were examined. All testing was performed in a laboratory under controlled conditions. Preliminary laboratory tests included flame spread evaluations, flame penetration, ignition temperatures, air permeability, and adhesion. Having established arbitrary cutoff values, the original 18 candidates were narrowed to 8. More specialized tests followed. The effects of water immersion and dry aging on flame spread performance and other physical properties were then examined. This Bureau of Mines report was written to provide information for those concerned with using rigid urethane foam as a sealant. Its intent is to describe the various laboratory evaluations performed and to delineate the performance of each candidate. This report neither promotes nor discourages the use of rigid urethane foams. It presents results that will enable those responsible for using or enforcing the use of rigid urethane foams in underground mines to make informed decisions.