This invention includes a pot unit having an outer periphery. The pot unit is constituted by a surface layer body, an outer surface layer, a spatial region, a water seepage hole, a gas flow path, a water injection unit, a sealing unit, a water drainage port, a stop part and a water level buffering region. The surface layer body is configured with a concave containing region. The outer surface layer is utilized to support the surface layer body. The spatial region is sandwiched between the surface layer body and the outer surface layer. The water seepage hole is communicated between the containing region and the spatial region. The gas flow path is communicated from the spatial region to the outer periphery. The water injection unit formed by an integrated covered protruding design is communicated from the spatial region to the outer periphery. The sealing unit is tightly sealed and combined with the water injection unit. The water drainage port is communicated from the containing region to the outer periphery. The stop part formed in an inward protruding manner is located at a lateral side of the water drainage port and faced toward an inner side of the containing region. The water level buffering region is formed between the stop part and an erecting plane of the containing region.
