To prevent whirling of dust in a storage warehouse and to prevent a liquid crystal substrate stored on a storage shelf from being contaminated by dust, by generating a flow of cleaning air over the whole area of the storage shelf.

Diffusion casings 52 of cleaning air outlet devices 5 are formed so that the cleaning air flowing therein is jetted out by being straightened and diffused, and arranged adjacently to each other to prevent a dead space without running the cleaning air from being produced.