A protective response which is initiated by an out-of-limit process condition that can cause injury or unacceptable environmental contamination. An instrument, or possibly software, which will not allow one part of a process to function unless another part is already functioning.
Reference: Adapted from CCPS (http://www.aiche.org/ccps/resources/glossary/process-safety-glossary/)
A system that detects out-of-limits or abnormal conditions or improper sequences and either halts further action or starts corrective action.
Reference: Interlock System definition by Guidelines for Pressure Relief and Effluent Handling Systems, CCPS, ISBN 978-0-8169-0476-1