As they had intimate knowledge of the Nazis' policy of mass murder, the Sonderkommando were considered Geheimnisträger — bearers of secrets — and as such, were held in isolation away from prisoners being used as slave labor (see SS Main Economic and Administrative Office).[11] Every three months, according to SS policy, almost all the Sonderkommandos working in the death camps' killing areas would be gassed themselves and replaced with new arrivals to ensure secrecy. However, some inmates survived for up to a year or more because they possessed specialist skills.[12] Usually the task of a new Sonderkommando unit would be to dispose of the bodies of their predecessors.