Metal detectors show up as the designated Critical Control Point on the overwhelming majority of packaged food HACCP plans, and auditors know exactly where to look first. A missed sensitivity check, a test piece that does not match the product on the line, or a phase setting that has quietly drifted out of range is enough to turn a routine walkthrough into a corrective action plan. Most plants can produce the SOP for the metal detector; far fewer can produce proof that every scheduled check actually happened on time, every shift, on every line. This guide breaks down how CCP metal detector verification is supposed to work, the sensitivity testing protocol auditors expect to see, and how a CMMS closes the gap between the checklist and the record. See how Oxmaint tracks every verification automatically inside a free trial.
Why This One CCP Gets the Most Auditor Attention
Metal detection sits at the very end of the line — the last control point before contaminated product reaches a customer. That position is exactly why it draws more scrutiny than almost any other step in a food safety plan.
What Makes Metal Detection a CCP, Not Just Good Practice
A step qualifies as a Critical Control Point when it is the last point where a physical hazard can be controlled before the product ships. For packaged food, that is almost always the metal detector: raw materials have already passed through magnets and sieves, processing is finished, and the only remaining check before the case is sealed is the detector head. Once that step is classified as a CCP, the rules change — critical limits must be defined, every check must be logged, and any failure requires a documented corrective action, not a quiet re-run.
This is also where sensitivity and calibration get confused. Calibration is a service event performed by a technician or the equipment provider. Verification is the routine test — run by the operator or QA — that confirms the detector still catches ferrous, non-ferrous, and stainless steel contaminants at the sensitivity level the HACCP plan requires. Auditors ask for both records separately, and a plant that only has calibration certificates on file is missing the verification trail entirely.
The Sensitivity Verification Protocol, Step by Step
BRCGS Issue 9, Clause 4.10.3.4 requires routine checking of metal detection equipment, with the HACCP team setting the exact frequency for the site. This is the sequence most food safety teams build their checklist around.
Start of shift, every 30 minutes to 2 hours during the run, after any stoppage longer than 15 minutes, after a product changeover, and after any maintenance touches the detector.
Run certified ferrous, non-ferrous, and stainless steel test pieces through actual product, not an empty belt, at leading, center, and trailing positions.
A detector that signals but fails to physically reject the product is still a failed test. Both mechanisms must be verified on every pass, not assumed from the last check.
If a test fails, every unit made since the previous successful verification is placed on hold and re-screened before it can move. This is the step most paper systems execute inconsistently.
Record detector ID, product code, test piece certificate numbers, pass or fail per position, operator name, and QA sign-off — tied to the specific CCP, not a loose maintenance note.
Paper Verification Logs vs. CMMS-Enforced Checks
The gap between a clean audit and a Critical finding usually is not the protocol — it is whether the protocol was actually followed on every shift, on every line, without exception.
| CCP Requirement | Paper Checklist | Oxmaint CMMS |
|---|---|---|
| Test frequency compliance | Depends on the operator remembering the interval during a busy shift | Automatic reminders and scheduled checks tied to the CCP interval |
| Test piece traceability | Certificate numbers rarely logged against the actual test event | Test piece certificates linked to every ferrous, non-ferrous, and SS check |
| Failed test hold procedure | Manual hold tags; product sometimes released before re-screening | Hold status enforced in the system until re-verification is logged |
| Phase setting change history | Not tracked unless a technician happens to note it | Every phase and sensitivity adjustment timestamped and attributed |
| Audit record retrieval | Hours of searching binders across shifts and lines | Full CCP history by detector, date range, or product in seconds |
Where Verification Programs Actually Break Down
The 2-hour interval looks fine on paper. On a line running behind schedule, it quietly stretches to three or four hours, and nobody flags the gap until an auditor does the math on timestamps.
A service technician's calibration certificate is not a substitute for the routine test piece check. Auditors ask for both, and plants that only have one on file get flagged immediately.
Product moisture, temperature, and packaging changes all shift the ideal phase setting. When technicians adjust it informally, sensitivity can silently degrade below the critical limit.
Without a system enforcing the hold, product made since the last good test sometimes ships before re-screening is complete — turning a caught deviation into a real recall exposure.
What Changes Once Verification Is CMMS-Enforced
Frequently Asked Questions
Why is a metal detector almost always a CCP in a food HACCP plan?
How often should sensitivity be verified on an active line?
What test pieces are required for a valid CCP check?
What happens when a sensitivity test fails?
How does a CMMS improve metal detector CCP compliance?
Stop Finding Out About a Missed Check During the Audit
A sensitivity test that did not happen on schedule is invisible until an inspector asks for the log. Oxmaint schedules every ferrous, non-ferrous, and stainless steel check, enforces the hold on a failure, and keeps the full CCP record ready before anyone has to go looking for it.
