1 : A safeguarding method used to prevent unplanned releases of toxic or hazardous compounds into uncontrolled work areas. [SEMATECH]
2 : level of containment that is external to and separate from primary containment . Secondary containment is a method of safeguarding used to prevent unauthorized releases of toxic or hazardous gases into uncontrolled work areas. Secondary containment means those methods or facilities in addition to the primary containment system. [SEMI F6-93]
