Solid state fermentation is an alternative to use low cost agro industrial residues to produce enzymes in packed bed bioreactors (PBB). One of the main problems in operating these systems is the lack of criterion to guide the bioreactors scale up and airflow rate for each arrangement. Thus, the airflow rate calculated based on modified Damköhler number equal to one is distributed in two points of the bed and inserted entirely on the bottom of it, so as to find better conditions for running the system. For the assays with air distribution, the maximum xylanase activities were obtained in the 1st and 7th modules, equivalents to 2000 and 1700 U/g.d.s. Without air distribution, the maximum xylanase activities were 1600 and 1200 U/g.d.s., correspondent to the 7th and 8th modules. For CMCase activities, the maximum production was obtained in the 7th and 8th modules, equivalents to 240 and 210 U/g.d.s. for assays with air distribution, and 1st and 7th modules for assays without air distribution, equivalents to 230 and 220 U/g.d.s. The strategy didn’t bring up good results, however the technique of distributing the airflow rate showed up a good strategy for scale-up packed bed bioreactors, and it must be investigated.