Why are there mezzanines between the first and second floors of some buildings?

There are many reasons for setting the interlayer. From a purely technical point of view, there are the following reasons: sound insulation, heat insulation, waterproofing, installation of equipment or electrical pipelines, and use of professional technology (such as tangible document transmission, letter transmission, vacuum pipeline in airport stations or baggage and mail transmission, etc.). ). According to Party A's special requirements, there are two unnecessary reasons: confidential use (such as the refuge passage or refuge room commonly used in confidential projects), and some developers use it to steal the area in the planning opinions. In addition, in the super high-rise building, you can also see the setting of the refuge floor. Strictly speaking, this should not be called mezzanine.