The site needs to implement a good Operational and Readiness Inspection procedure. System inspection deficiencies need to be identified, and (if possible) reviewed by a second party before future tests are conducted. This inspection could include the following:

Check all relief valve set points
Check potential design flaws
Check all other relevant operational characteristics

A proper vent system design is as important as the relief valve itself. A vent system should be able to operate with no consequence at all. Proper facility design and venting to a safe location would have made this a near-miss instead of an incident.