Pack-Off Isolators To achieve Operator Exposure Levels (OELs) below 1µg/m³, it is necessary to apply a method of barrier isolation to the process. As a fully enclosed pack-off system, this incorporates both primary and secondary methods of containment and ensures that good ergonomics and operability are prime considerations. Single chamber isolators are available that utilise continuous liners although where single liners are used, it is most common to apply a double chamber design.