"A second underground coal gasification experiment is being conducted at the Laramie Energy Research Centers field site near Hanna, Wyoming. This paper presents the results from the first phase of this Hanna II experiment in which coal seam permeability was evaluated, pneumatic linking and linking via reverse combustion were studied, and a sustained gasification process was maintained between the two linked vertical wells. Extensive in situ and surface process instrumentation have provided considerable information on the chemical and physical mechanisms involved in underground coal gasification, Air injection alone did not increase permeability to levels which would allow sustained gasification, Reverse combustion linking was determined to be a local, relatively low temperature process which advanced at a 5 ft/day rate and produced a high permeability carbonized path , Subsequent gasification was completed over a 38 day period. Overall, injection of 1,9 MM scf/day of air yielded 2.7 MM scf/day of gas with a heating value of 152 Btu/scf. Material balance calculations indicate that 1688 tons of coal in place were utilized. Specific discussions of reaction front configurations and interpretation of in situ thermometry are included."