NC-ARC-0312 Exception record Rev 3

Humidity Excursion - Bay 4B

Identifier: NC-ARC-0312 Rev 3
Location: Bay 4B, Level 4 stacks; 1,290 m
Opened: 2026-04-17
Closed: 2026-04-19
Affected holdings: None confirmed

1Sequence

Time	Record
17 Apr / 06:20	Bay 4B upper sensor exceeded the preservation work-band.
17 Apr / 06:44	Adjacent sensors remained within band; aisle isolated from routine retrieval.
17 Apr / 09:10	Supply damper linkage found partially disengaged.
18 Apr / 14:30	Linkage replaced; environmental readings stabilized.
19 Apr / 11:00	Sampled enclosures cleared by Archive Preservation.

2Holding review

Eleven enclosures nearest the upper sensor were inspected for dimensional change, adhesion, corrosion, and odor. No change was recorded. The enclosures were returned to their prior positions after shelf locations were reconciled against the retrieval ledger.

3Disposition

The event is closed as an equipment-maintenance exception. The affected sensor remains in service. The damper linkage has been added to the six-month visual inspection route.

4Limitations

Inspection was by sampling and cannot establish the condition of every sheet, plate, or storage medium in Bay 4B. No sealed enclosure was opened. This record does not change the archive holding count.