Summary
In short
- A metal detection check is the routine verification that a detector still rejects certified test pieces at its validated sensitivity, and it is the evidence a GFSI auditor asks for first.
- Validation and verification are different activities: validation proves the detector can control the hazard under worst-case conditions, verification proves it still does. This template is verification.
- BRCGS Issue 9 clause 4.10.3.1 requires in-line detectors to incorporate an automatic rejection device or an equivalent controlled fail-safe, and SQF requires a documented foreign body prevention programme with critical limits and corrective actions.
- Test pieces must pass through the least sensitive part of the aperture, which is usually the geometric centre, and at production line speed rather than a slow hand pass.
- A failed check requires quarantine of all product back to the last passing check, so check frequency is in practice a decision about the size of the hold you can absorb.
- Phase angle must be reset and reverified after every product changeover, because product effect from moisture, salt and conductive ingredients can mask a contaminant signal.
What it is
What is a metal detection check?
What is a metal detection check?
A metal detection check is a routine test in which certified ferrous, non-ferrous and stainless steel test pieces are passed through a working metal detector to confirm it still detects and rejects at its validated sensitivity. It is run at start up, at defined intervals during production, and at the end of a run.
What is the difference between validation and verification for a metal detector?
Validation proves the detector is capable of controlling the hazard, established once under worst-case conditions of product, orientation and line speed. Verification proves it is still doing so, and is the routine check recorded on this template. Auditors treat them as separate obligations and ask to see both.
When to use it
When is a metal detection check required?
Metal detection is only a CCP where your hazard analysis says it is. Running checks on a detector that your HACCP plan does not treat as a critical control creates records you must then defend, while a genuine CCP with a gap in its check record puts every run since the last good check in question.
Use it for
- Metal detection is identified as a CCP or preventive control in your HACCP plan and needs routine verification evidence
- A production run is starting, ending, or crossing a defined interval within the run
- A product changeover has occurred and phase angle and sensitivity need reverification for the new product
- The detector has been serviced, moved, or has had a parameter changed since the last check
- A reject was recorded and you need to confirm the detector and reject mechanism are still performing before restarting
Not for
- Annual or semi-annual verification by the manufacturer or a third party, which is a separate exercise with its own record
- Initial validation of the detector against a new product, which establishes the sensitivity this check then verifies
- X-ray inspection systems, which share the logic but have different test piece conventions and image-based failure modes
- Foreign body controls that are not metal, such as glass or hard plastic policies, which sit under a different clause
- Calibration of the test pieces themselves, which is certified by the supplier and tracked as a document, not a check
Standards
Which SQF and BRCGS requirements does this template satisfy?
This template records the routine verification required by GFSI benchmarked schemes. It does not establish the sensitivity it verifies, and it does not on its own constitute a foreign body prevention programme.
| Clause | Requirement | Where it lands |
|---|---|---|
| BRCGS 4.10.3.1 | In-line detectors incorporate an automatic rejection device, or an equivalent controlled fail-safe where automatic rejection is not practicable | Reject mechanism confirmation |
| BRCGS 4.10.3 | Routine verification of detection and rejection using certified test pieces, with documented results and corrective action | Test pieces |
| SQF 11.2 | Documented foreign body prevention programme with defined critical limits and corrective action procedures | Header and coverage |
| SQF 11.7 | Monitoring records signed by a responsible person | Sign-off |
| HACCP principle 4 | Establish monitoring procedures for each critical control point | Check frequency and result |
| HACCP principle 5 | Establish corrective action when monitoring shows a deviation | Hold and release |
| ISO 22000 cl.8.5.4 | Hazard control plan with monitoring and correction defined | Whole record |
What it does not cover
- Initial validation against a new product or packaging format, which establishes the detection limits this check verifies and is usually done with the manufacturer.
- Periodic third-party verification, which most sites run every six to twelve months and which examines the detector itself rather than its daily performance.
- The foreign body prevention programme as a whole, which also covers glass and hard plastic policy, screening, and supplier controls.
- Hold and release of affected product, which needs its own record with disposition and authorisation.
Audit findings
Most common metal detection audit findings
Metal detection findings cluster in a small number of places, and almost all of them are about the gap between what the detector can do and what the record proves it did.
| Finding | Clause | What fixes it |
|---|---|---|
| Sensitivity or reject threshold does not match the validated setting for the product being run. Unauthorised parameter changes between shifts are a recurring finding. | BRCGS 4.10.3 | Record the running parameters on every check and compare them against the validated settings for that product code. |
| Phase angle not reset or reverified after changeover, so product effect masks the contaminant signal. | BRCGS 4.10.3 | Trigger a check on every changeover, with phase verification as a required field rather than an optional note. |
| Check performed but no record of where in the aperture the test piece passed. | HACCP principle 4 | Record aperture position and confirm the pass was through the least sensitive region at line speed. |
| Failed check recorded with no corresponding quarantine of product back to the last good check. | HACCP principle 5 | Auto-open a hold record on any fail, scoped to the window since the previous passing check. |
| Reject mechanism not tested, only detection. The detector saw the piece but nothing proves it was removed. | BRCGS 4.10.3.1 | Confirm the reject actuated and the piece reached the locked reject bin, as separate fields. |
| Test pieces uncertified, damaged, or with no traceable certificate on file. | BRCGS 4.10.3 | Hold certificates as controlled documents and reference the test piece ID on each check. |
| Checks signed by someone not authorised as a responsible person under the programme. | SQF 11.7 | Restrict sign-off to a trained and named role, enforced by the form rather than by convention. |
| End of run check missing, so the last portion of the run has no verification bracket. | HACCP principle 4 | Make the end of run check a required step in the run closure workflow. |
| Fault or error codes present in the control panel log and not cleared before production. | BRCGS 4.10.3 | Add a control panel status check to the start-up record, with faults blocking start. |
| Check frequency defined in the plan but not actually achievable given line speed and hold capacity. | HACCP principle 5 | Set frequency from the volume you can absorb on a hold, then hold the line to that interval. |
Worked case
What a failed check actually costs
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By jurisdiction
How the duty differs by jurisdiction
Foreign body detection is governed by private certification schemes rather than statute, which makes the applicable requirement a function of who audits you rather than where you operate.
BRCGS Issue 9 cl.4.10; SQF; FSSC 22000
Certification requirement. Routine verification with certified test pieces, documented results and corrective action.
The audit standard your customers require determines the detail. BRCGS is the most prescriptive on detection equipment.
FSMA Preventive Controls; 21 CFR 117
Hazard analysis driven. Where metal is a hazard requiring a preventive control, monitoring, corrective action and verification are mandatory.
Metal detection is a process preventive control with its own monitoring and records requirements.
Regulation (EC) 852/2004; HACCP principles
HACCP based. Foreign body control is required where hazard analysis identifies it.
National enforcement, with retailer codes usually setting a higher bar than the regulation.
ISO 22000 cl.8.5.4
Hazard control plan with monitoring and correction defined for each control measure.
Certification auditors look for the link from validation through verification to corrective action.
Definitions
Metal detection definitions and key terms
- Critical control point (CCP)
- A step where control is essential to prevent or reduce a food safety hazard to an acceptable level. Metal detection is a CCP only where the hazard analysis says so.
- Validation
- Evidence obtained once that the control is capable of achieving the required result under worst-case conditions of product, orientation and line speed.
- Verification
- Routine evidence that the validated control is still performing. This template is a verification record.
- Test piece
- A certified sphere of ferrous, non-ferrous or stainless steel at the validated detection limit, usually carried in a card or stick with a traceable certificate.
- Product effect
- The electromagnetic signal generated by the product itself. Moisture, salt and conductive ingredients produce strong signals that can mask a contaminant.
- Phase angle
- The setting that separates the product signal from a metal signal. Set per product and reverified after every changeover.
- Least sensitive region
- The part of the aperture where detection is weakest, usually the geometric centre. Test pieces must pass through it for the check to be meaningful.
- Hold and release
- Quarantine of all product back to the last passing check following a failure, with a documented disposition decision before any release.
FAQ
Frequently asked questions about metal detection checks
How often should a metal detector be checked?+
At start up, at defined intervals during the run, at the end of the run, and after any changeover or parameter change. The interval itself should be derived from how much product you can afford to quarantine, since a failure puts everything back to the last passing check on hold. Hourly is common on high-value lines; two to four hours is common elsewhere.
What size test pieces should we use?+
The sizes established by your validation for that product, not a generic figure. Published guidance for dry products commonly cites the region of 1.5mm ferrous, 2.0mm non-ferrous and 2.5mm stainless as achievable minimums, but wet, salted and conductive products need product-specific validation because of product effect, and the achievable limit is often larger.
What happens if a metal detection check fails?+
Quarantine all product back to the last passing check, since nothing indicates when detection stopped working. Investigate the cause, confirm the detector and reject mechanism after any correction, run a passing check before restarting, and record the disposition of the held product before any release.
Does the reject mechanism need testing separately from detection?+
Yes. Detection and rejection are separate functions and a detector can register a contaminant without the reject actuating. BRCGS clause 4.10.3.1 addresses the rejection device specifically. Record both that the detector signalled and that the piece was physically removed to a secured reject location.
Is metal detection always a CCP?+
No. It is a CCP only where your hazard analysis identifies metal contamination as a significant hazard controlled at that step. Where it is a prerequisite or a customer requirement rather than a CCP, the checks still matter but the critical limits, monitoring and corrective action obligations attach differently.
Who is allowed to sign off a metal detection check?+
A responsible person as defined in your programme, which normally means someone trained on the detector and named in the plan. SQF requires monitoring records to be signed by a responsible person, and checks signed by unauthorised staff are a recurring finding even where the check itself was done correctly.
The agents
What the agents do with it
The check itself takes ninety seconds. What fails is everything around it: the interval that slips on a busy shift, the changeover nobody flagged, the failed check where the hold never got opened.
Schedules checks against the interval in your plan, blocks run closure until the end of run check is recorded, and opens a hold automatically on any fail, scoped back to the last passing check.
Watches the asset record. A service, a move or a parameter change on the detector triggers a reverification task before the line runs again.
Holds the responsible person roster, so sign-off is restricted to trained and named staff and expiring competencies surface before they lapse.
Rolls check completion, deviation counts and open holds into one view, and holds every write for your approval.
This template lives in KnowQuality — quality and food safety. HACCP, nonconformance, traceability, laboratory and customer complaints.
Sources
Sources
- BRCGS Global Standard for Food Safety, Issue 9, clause 4.10 (foreign body detection)
- SQF Food Safety Code, foreign body prevention and monitoring record requirements
- Codex Alimentarius HACCP principles 4 and 5, monitoring and corrective action
- ISO 22000:2018 clause 8.5.4, hazard control plan