This is so that, if there is any small breach in the citadel, the pressure tends to blow away and outwards any harmful agents and to prevent their entry.
Kungoko, ukuba ulwaphuko kancinci kwinqaba yesixeko, uxinzelelo olwenza uthandeko lokuphaphatheka kanye nokuphumela ngaphandle nakuluphi ulwenzakaliso ukukhusela ukungenisa.