8.4 Containment Playbook: Suspect Lots, Line Stop Triggers & Escape Handling

When a defect is detected, the immediate priority is not Root Cause Analysis; it is Containment. You cannot investigate a fire while the building is still burning. This chapter defines the emergency protocols to "stop the bleeding"—isolating the risk, defining the suspect population, and establishing a Clean Point before production resumes.

Defining the Suspect Lot (The Bracketing Logic)

A "Suspect Lot" is the volume of production that might be affected, bounded by the last known good state and the detection point.

The "Bookend" Principle:

To quarantine effectively, you must identify the "Bookends" of the risk window.

Start Point (Bookend A): The last verified "Good" event (e.g., the last passing hourly audit, the last setup verification, or the last Golden Sample run).
End Point (Bookend B): The moment of detection + the current WIP (Work In Progress).

Logic Flow:

If defect is continuous (e.g., broken tool) -> Then Quarantine ALL units back to Bookend A.
If defect is random/intermittent -> Then Quarantine the entire shift production for 100% sorting.
If traceability is poor (no serial numbers) -> Then Quarantine the entire Work Order.

Pro-Tip: Never trust the "feeling" that "it just started." Without data, the start point is always the last time you successfully validated the process.

Line Stop Triggers (The Andon Protocol)

Operators must have the authority and the mandate to stop production without fear of reprisal. Ambiguity here leads to large scrap piles.

Hard Triggers for Immediate Stop:

Severity 1 Defect: Any safety violation (e.g., exposed high voltage, toxic leak).
Consecutive Failures: 3 consecutive units fail for the same defect.
Yield Drop: First Pass Yield (FPY) drops below 90% in a single hour.
Process Drift: A Critical to Quality (CTQ) parameter (e.g., reflow temperature) moves out of control limits (Cpk < 1.0).

Action:

If Trigger conditions are met -> Then Stop the conveyor/machine.
If Line is stopped -> Then Illuminate Red Andon Light and page the Quality Engineer.
Constraint: Production CANNOT resume until the Quality Engineer signs off on the "First Good Piece" after adjustment.

Escape Handling (Customer Protection)

An "Escape" is a defect that has left the factory control (shipped or moved to the next tier). Speed is the only variable that mitigates damage.

Step 1: The Alert (Notification)

If Safety/Regulatory Risk -> Then Notify Customer within 24 hours (Legal Requirement).
If Functional/Cosmetic Risk -> Then Notify Customer immediately with a containment plan (don't wait for the root cause).

Step 2: The Clean Point

You must visibly distinguish "Safe" product from "Suspect" product to restore customer confidence.

Action: Mark all certified safe units (produced after the fix or screened 100%) with a specific identifier (e.g., Green Dot, "C" stamp) on the packaging or unit label.
Communication: Send an "Alert Notice" to the customer detailing the marking convention: "All units with Green Dot on the box are certified free of Defect X."

Step 3: Inventory Sweep

If Escape is confirmed -> Then Check three locations immediately:
1. Finished Goods Warehouse: Stop current shipments.
2. In-Transit: Recall or divert shipments if possible.
3. Distributor Hubs: Issue a stock hold.

100% Sorting (Firewalling)

When a process is unstable, you must install a temporary Firewall (Human or Machine) to protect the customer.

Rules of Engagement:

Instruction: Create a "One Point Lesson" (visual aid) specifically for the defect. Do not rely on general inspection criteria.
Efficiency: Sorting is fatiguing. Rotate inspectors every 2 hours to maintain attention.
Exit Criteria: The Firewall remains in place until the Root Cause is eliminated AND 3 consecutive production lots pass with zero defects.

Final Checklist

Parameter	Rule / Threshold
Suspect Scope	Back to the "Last Known Good" check (Audit/Setup).
Line Stop Rule	3 Consecutive Fails OR Safety Risk = Immediate Stop.
Restart Authority	Only Quality Engineer or Manager can authorize restart after a Stop.
Clean Point	Must be visually distinct (Green Dot/Stamp) on unit/box.
Notification	Safety issues = < 24 Hours.
Firewall Exit	3 Clean Lots + Verified Root Cause Fix.
Traceability	If specific serials cannot be identified, the whole Lot is guilty.