The Clean Zone is located within Gnomeregan, and lies just beyond the Hall of Gears' upper level. It is the last remaining area where gnomes unaffected by the radiation have a holding. They have posted guards to defend the area against troggs, which can be found both in the Dormitory below, and in the upper levels of the Hall of Gears, above.
The Clean Zone has a mailbox, an engineering vendor (Tink Sprocketwhistle), medics, and technicians that range from level 29 to 30 (elite). It also has a few Sparklematic 5200s, where can be cleaned up.