Problem Solving & Quality · Contain

Suspect Lot Quarantine

Trace every lot made since the last known good one, block it physically and in the system, and define the clean break point.

Time45 min
FormatSmall group
StageContain

Suspect Lot Quarantine: what it is and why it works

Suspect lot quarantine identifies, blocks and dispositions every lot that could carry a defect. It starts from the last lot known to be good, with evidence, and lists everything produced since then wherever it sits: in process, in stock, in transit or at the customer. Those lots are blocked both physically (tags, segregated areas, locked valves) and in the ERP, and a clean break point is defined as the first lot made after containment took effect. Each suspect lot then receives a recorded disposition: sort, rework, release by test or scrap.

Quarantine turns a vague fear that 'some batches might be bad' into a bounded, traceable list, which is the first thing customers and regulators ask for. It works only as well as traceability does: lot genealogy, batch records and shipping records must link raw materials to finished product and to destinations. Quarantine is the product side of containment; immediate containment actions protect future output, while quarantine deals with output already made. Stratification of test results across suspect lots often narrows the affected population, and the break point later informs the control plan. ISO 9001 requires control of nonconforming outputs, but good practice goes further on speed, because every hour lets more product move.

What you need

Evidence for the last known good lot: test results, retained samples
Lot genealogy and traceability records from raw material to shipment
ERP access to block inventory
Physical means: tags, a segregated area, locks
Contacts at customers, carriers and distribution for product already shipped

What you get

A complete list of suspect lots and their locations
Physical and system blocks on each lot
A defined clean break point
A recorded disposition for each lot, with its approver
A measure of traceability performance: the time taken to build the list

When to use it

When nobody can say which batches, tanks or shipments are affected.

How to do it, step by step

Find the last lot, batch or date known to be good, with evidence.
List every lot produced since then, wherever it is: in process, in stock, in transit, at the customer.
Block them in the ERP and physically — red tags, segregated area, locked tank valves.
Define the clean break point: the first lot made after the containment is in place.
Decide the disposition of each suspect lot — sort, rework, release by test, scrap — and record it.

Worked example: High viscosity in a lubricant blending plant

Illustrative scenario — figures are realistic but not from a real company.

A lubricant blender finds that a retained sample of ISO VG 46 hydraulic oil tests at 51 cSt at 40 °C, above the 41.4 to 50.6 cSt range for the grade. The plant blends around 40,000 gallons a day into drums, totes and bulk tankers, and the result came in three days after blending.

Last known good: batch 2311, with a full certificate and a retained sample retested in specification. Everything blended after it in the same tank was suspect.
Listing: an ERP genealogy query showed six batches since 2311: two still in tanks, 1,100 drums in the warehouse, 48 totes in transit and two bulk loads already delivered to distributors.
Blocking: all lots were set to 'blocked, quality' in the ERP, tank outlet valves were locked and tagged, and drums were moved behind a red chain. Customer service reached both distributors and the carrier within two hours.
Break point: a passing base-oil valve was found and repaired; the first batch blended after the repair, and tested in specification, was defined as the clean break.
Disposition: every suspect batch was tested. Three were in specification and released with certificates, two were corrected by reblending, and one was downgraded to a different grade.

Result. No out-of-spec oil reached end users. Building the suspect list took 90 minutes, mostly because tote shipments were tracked on a spreadsheet outside the ERP. Bringing those shipments into the system became a separate improvement action.

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Common pitfalls and how to avoid them

Starting from the first bad lot found instead of the last good lot.The defect may have started well before it was detected; work forward from the last lot proven good.
Blocking only in the system.Tag and segregate physically too; forklift drivers do not read ERP status.
Forgetting material in transit and at customers.Include shipped lots in the list and notify customers promptly, following contract and regulatory requirements.
Undocumented disposition decisions.Record each disposition, the evidence behind it and who approved it; release by test needs a sound sampling plan.

Frequently asked questions

What is a clean break point?

The clean break point is the first lot, batch or serial number produced after the containment or correction was in place and verified. Everything from the last known good lot up to the break point is suspect; everything after it is considered clean. Defining it explicitly lets you release new production with confidence and tells customers exactly which lots they need to check.

How do you decide what to do with quarantined product?

Base each decision on evidence and risk. Options include release by test when a sound sampling plan shows conformance, sorting to remove defects, rework to a controlled procedure, downgrading to a less demanding use, or scrap. Customer approval is often required for deviations or rework. Record the decision, the supporting data and the approver for every lot.

How fast should a quarantine list be built?

As fast as possible, ideally within about an hour for product still on site. The longer it takes, the more product moves and the larger the eventual sort or recall becomes. If building the list is slow, treat that as a traceability problem in its own right and address it once the incident is over.

Origin

Control of nonconforming product and lot traceability — standard quality-management practice (ISO 9001); no single author.

Used in these playbooks

Quality alert: the first 24 hours 1 day

One day to take control of a fresh incident: make safe, protect the customer, block every suspect lot, keep the evidence intact and pin down where the problem is — and is not.

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