An initial attack model was sensitive to changes in production rate of suppression forces, as shown by changes in final fire size. The adequacy of fireline construction rates used in fire planning models has been questioned. A fire containment model was tested over a range of suppression force productivities to show the effect on final fire size. The percentage of fires that escaped was sensitive to the productivity of line-building units. The degree of sensitivity depended on the severity of environmental conditions. Final fire size was most affected by fireline construction rates under the most severe environmental conditions tested. Using distributions of production rates from weighted averages of the results produced final fire sizes similar to those obtained using point estimates in the simulation model. Planners may be able to use graphs like those presented, in place of iterations of a fire containment model.