How often does a DHA need to be updated?

Begin with the prior report. Confirm what areas and operating modes it covered, which materials and tests it relied on, which standard edition it used, and whether its recommendations have traceable dispositions. A report can remain valuable historical evidence while no longer being sufficient as the current basis.

An update may be bounded when the affected system and assumptions are clear. A new or substantially rebuilt analysis may be more defensible when the old scope is uncertain, records are missing, major processes changed, or the earlier method cannot be reconciled with the present facility. The label matters less than a documented scope that closes the real gaps.

Keep a change register connected to the DHA rather than waiting for a future date. Record who screened each change, what evidence was reviewed, what decision was made, and whether a specialist follow-up is open. Confirm the current NFPA 660 text and applicable authority requirements for the actual facility; this page does not set a universal due date or determine compliance.