The known sources of infection were nothing new; the promotion rules publicly visible at the inspection station were for outsiders, while internally, the standards were much more stringent and harsh.
From the third-phase onwards, it's basically "one radish per pit," competing not just on professional ability, but on genuine intelligence and achievements.
The ability to go on field missions to bring supplies to Happiness City and generate revenue for the inspection station is one aspect, but the key is to have demonstrable hard achievements.
And "containing the source of infection" happens to be one of the core indicators for evaluating an inspector's ability.
The current fifth-stage inspector must have contained three "destruction" level sources to ascend, the fourth-stage must have contained at least one "destruction" level, and even the third-phase must gather five "disaster" level plus a bunch of "plague" level sources to qualify.
