The only difference might just be a slightly smaller space.
Mainly because the structure of the safe house's walls is rather special, usually consisting of multi-layered composite structures. Besides specially formulated concrete, there are fireproof layers, insulation layers, bulletproof steel plates, and explosion-proof panels, which can easily withstand sniper rifles, machine gun fire, and bomb attacks, effectively blocking forced entry for two hours.
More advanced safe houses can even resist chemical, biological, and nuclear weapon radiation.
This concept originated during the U.S. Civil War, initially used to rescue black slaves and eventually evolved into a dedicated facility for intelligence agencies and law enforcement agencies, used for providing accommodation to special agents, spies, and witness protection.
In our country, there are also many professional teams designing and building such safe houses.
