PAN-FSR-2091-051
Tier 3 escalation: quarterly containment-integrity test on BSL-4 Vault cell PAN-7 detected a negative-pressure deviation outside specification. Cell isolated, Director notified, root cause identified as a degraded HEPA filter gasket. Cell remains offline pending Director sign-off on return to service.
Fault Description
During the quarterly BSL-4 Vault containment-integrity test on 2091-05-16, cell PAN-7 recorded a negative-pressure reading of −38 Pa against the specification of −50 Pa ± 5 Pa (acceptable range: −45 to −55 Pa). The integrity test pressurises each cell to its rated negative differential and measures pressure-decay rate over a 30-minute hold period. PAN-7's pressure decayed from −50 Pa to −38 Pa over the 30-minute window — a decay rate of 0.4 Pa/min, exceeding the maximum allowable rate of 0.15 Pa/min. This indicates an air-leakage path that, while not constituting a containment breach under operational conditions (the cell's exhaust HEPA system continuously maintains negative pressure), degrades the cell's ability to maintain containment in the event of an exhaust-fan failure or power interruption.
Per SOP PAN-ENG-044 (BSL-4 Vault Containment Integrity), any cell failing the quarterly pressure-decay test is immediately isolated, all biological materials are transferred to an adjacent cell under two-person protocol, and the FSR is auto-escalated to Tier 3 with mandatory Director notification. The Director of Continuity was notified at 07:42 on 2091-05-16.
Root Cause Analysis
Dr. I. Crane (Head of Strain Engineering, as the Vault's designated scientific authority) and N. Chandra (Facilities Engineer) entered cell PAN-7 under two-person protocol at 09:00 on 2091-05-16, after biological materials had been transferred to cell PAN-6. The investigation followed the containment-leak diagnostic procedure (SOP PAN-ENG-044, Annex C):
Step 1 — Door-seal test. The cell's entry-side and pass-through-side door seals were tested with an ultrasonic leak detector. Both seals returned readings below the background threshold — no leakage detected. Door-seal compression verified within specification on both doors.
Step 2 — Penetration-seal test. All service penetrations (electrical conduit, gas supply, liquid waste drain, communication cable) were tested with the ultrasonic detector. No leakage detected at any penetration.
Step 3 — HEPA housing test. The exhaust HEPA filter housing (housing EX-PAN7-01) was tested. The ultrasonic detector registered a signal at the gasket interface between the HEPA filter frame and the housing seal — specifically along the lower-right quadrant of the gasket. Visual inspection confirmed that the gasket (a closed-cell neoprene compression gasket, P/N CV-HG-BSL4) had developed a compression set in the lower-right section, reducing its effective thickness from the nominal 6mm to approximately 3.8mm. This allowed a small but measurable air-leakage path around the HEPA filter frame — sufficient to cause the observed pressure-decay rate but not sufficient to bypass the HEPA filtration itself (the filter media remained intact and undamaged).
Root cause: Gasket compression set due to age and sustained mechanical load. The gasket was installed 26 months ago (PAN-FSR-2089-041). The manufacturer's recommended replacement interval is 24 months. The gasket exceeded its service life by 2 months due to a scheduling gap in the preventive-maintenance calendar — an administrative failure, not a materials failure.
Work Performed
N. Chandra performed the corrective work on 2091-05-17 under SOP PAN-ENG-044 and the specific authorisation of the Director of Continuity (authorisation reference DC-AUTH-2091-017):
1. HEPA filter removal. Exhaust HEPA filter (P/N CV-HEPA-BSL4-EX, S/N H4-2089-027) removed from housing EX-PAN7-01 under bag-in/bag-out protocol per SOP. Filter visually inspected — media intact, no visible damage or penetration. Filter logged for incineration per standard BSL-4 waste protocol.
2. Gasket replacement. Degraded neoprene gasket removed from the housing seal face. Housing seal surface cleaned and inspected — no damage or residue that would affect the new gasket's seating. New gasket (P/N CV-HG-BSL4, from Vault containment stores) installed. Gasket compression verified with the housing's torque-limited clamping bolts — all 12 bolts torqued to 8.5 Nm per specification.
3. New HEPA filter installation. Replacement exhaust HEPA filter (P/N CV-HEPA-BSL4-EX, S/N H4-2091-003) installed under bag-in/bag-out protocol. Filter seated and clamped. DOP (dioctyl phthalate) aerosol challenge test performed on the installed filter: penetration 0.003% (specification: ≤0.01%). Filter confirmed to meet H14 classification.
4. Containment-integrity retest. Cell PAN-7 repressurised to −50 Pa and held for 30 minutes. Final pressure: −49.2 Pa. Decay rate: 0.027 Pa/min — well within the 0.15 Pa/min maximum. The cell passes the containment-integrity specification.
5. Cell restoration. Cell PAN-7 returned to operational-ready status pending Director sign-off. Biological materials remain in cell PAN-6 until Director authorises the return transfer.
Parts Consumed
1x HEPA filter, BSL-4 exhaust rated (P/N CV-HEPA-BSL4-EX) — drawn from Vault containment stores, Sub-level B3. Stock level reduced to 2 units; automatic reorder triggered. Lead time on BSL-4-rated HEPA filters: 6 weeks.
1x neoprene compression gasket, HEPA housing (P/N CV-HG-BSL4) — drawn from Vault containment stores. Stock adequate.
DOP aerosol challenge consumables — standard test consumables, drawn from QC stores.
Sign-off Chain
Investigation by: Dr. I. Crane, Head of Strain Engineering & N. Chandra, Facilities Engineer — 2091-05-16
Corrective work by: N. Chandra, Facilities Engineer — 2091-05-17
Containment retest witnessed by: Dr. I. Crane — 2091-05-17
Pending: Director of Continuity review and return-to-service authorisation
Post-Action Notes
The root cause — a HEPA housing gasket exceeding its manufacturer-recommended service life by 2 months — represents a preventive-maintenance scheduling failure. The Q1 2091 maintenance calendar did not include the PAN-7 exhaust HEPA gasket replacement because the 24-month interval was calculated from the installation date (2089-03-20) and the resulting due date (2091-03-20) fell between the Q1 and Q2 scheduled maintenance windows. The facilities scheduling system has been updated to flag any containment-critical component due date that falls outside a scheduled maintenance window, with automatic advancement to the preceding window.
The biological-safety risk from this event was negligible. The gasket degradation reduced the cell's passive containment margin (the ability to maintain negative pressure without active exhaust) but did not compromise active containment — the exhaust HEPA system was functioning normally throughout, and the air leakage path was around the filter frame gasket, not through the filter media. No biological material was exposed and no containment boundary was breached. The Tier 3 escalation reflects the Directorate's policy that any deviation on BCL-4 infrastructure is treated as a serious event regardless of assessed risk — the appropriate response to a containment anomaly is never "it was probably fine."
The cell will remain offline until the Director of Continuity reviews this report and signs the return-to-service authorisation. The Vault continues to operate at full capability using cells PAN-1 through PAN-6; PAN-7's offline status does not affect current research programmes.