For process equipment mounted outside or close to an outside wall, explosion relief venting is a viable protection method. However, in order to protect the upstream equipment, it is vital that the protection method includes a means to mitigate propagation of flame and burning materials back upstream. This can be achieved by either using an active isolation system (chemical or mechanical), or by using a passive isolation valve. The passive explosion isolation valve is a self-actuating device, which provides a mechanical barrier to mitigate the propagation of flame and burning materials to upstream equipment.