PURPOSE: To attain the leakage check or a piping with a practical utilization pressure by interposing a high pressure cylinder for pressurization filled with the gas having high permeability in addition to the general high pressure cylinders and piping this high pressure cylinder for pressurization to respective relevant general high pressure cylinders.

CONSTITUTION: In this cylinder-box A housing plural general high pressure cylinders B1-B4, the high pressure bomb B5 filled with highly permeable gas for pressurization is interposed in addition to the above-mentioned general high pressure cylinders. This high pressure bomb B5 for pressurization B5 is piped to the general high pressure bombs B1-B4 respectively. Consequently, the cylinder-box where the leakage check of the piping in the cylinder-box is conducted at any time in the practical utilization pressure and the handling of a toxic gas is safely attained is realized to contribute for the development of the semiconductor industry.