Efficiency of the air circulation system of a rock bed heat accumulator is a key factor for its overall effectiveness. The objective of the paper was to compare the air flows through the complete air circulation system of such accumulator for different solutions of the sealing system. The experimental objects were three 3-sectional rock bed accumulators, of which one was made in a simplified way and then sealing was proceeded in stages, while two others were considered as maximally sealed. The changes of air flow measured near the fan pumping the air into were used as a measure of sealing effectiveness. It has been found that a simplification of sealing in a construction of the rock bed accumulator may result in almost twice higher air flow into the accumulator. The particular effects of simplifications depend on the location (mainly before or after the rock bed) and the location of accumulator’s section (the nearest or the farthest from the fan). The simplifications of sealing of pipe passages through rock bed thermal isolation and pipe connections in air collectors may cause in total about 28-47% of total plausible range of flow changes, while simplifications in arrangement of sealing foil around the rock beds of particular sections of accumulator may result in about 53-72% of total plausible range of flow changes.