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A maintenance log records every preventive maintenance task done on food plant equipment: what was serviced, when, by whom and what was found. Paired with an equipment calibration log that shows measuring instruments were checked against a reference, it gives auditors proof that equipment stays fit for food safety use. Both should be dated, signed and reviewed by a second person.
This guide covers what the regulations say, a preventive maintenance checklist you can adapt, a calibration log template, and how to handle a failed check. It builds on the equipment expectations in our guide to good manufacturing practices in food manufacturing.
What the Regulations Require
In the United States, 21 CFR 117.40 says food-contact equipment must be cleanable and kept in good repair, freezers and cold storage that hold food able to support microbial growth need an accurate temperature-measuring device, and instruments that measure or record temperature, pH, acidity, water activity or other controls on microbial growth must be accurate, precise and in good working order.
Where a preventive control depends on an instrument, 21 CFR 117.165 requires you to calibrate process monitoring and verification instruments, or check them for accuracy, and to set the method and frequency in written procedures. A preventive controls qualified individual (or someone under their oversight) must review monitoring and corrective action records within 7 working days, and calibration records within a reasonable time. 21 CFR 117.305 adds that records must show actual values, the date, the signature or initials of the person who did the work, and be made at the time of the activity.
GFSI-benchmarked schemes such as SQF and BRCGS also expect a maintenance program and calibrated measuring equipment. Check the current edition of your scheme's code for the exact clause wording that applies to your site.
Maintenance Log: What to Record
A useful maintenance log answers five questions for every task: which asset, what was done, when, by whom, and what the result was. Add a sixth, whether product was at risk, for any task that found a problem.
Preventive Maintenance Checklist by Frequency
The tasks below are examples. Set the real list and frequencies from your equipment manuals, your risk assessment and your history of breakdowns.
| Frequency | Example tasks | What to record |
|---|---|---|
| Daily (pre-operation) | Guards and covers in place, no leaks, no loose parts, metal detector or X-ray tested with test pieces where used | Pass/fail, initials, time |
| Weekly | Lubricate per schedule, check belts and chains, inspect seals and gaskets on food-contact equipment, check conveyors for wear | Result, parts replaced, initials |
| Monthly | Refrigeration coils and door seals, compressed air filters, drive and bearing inspection, check fasteners on food-contact surfaces | Findings, work order or repair reference |
| Quarterly or annually | Service contractor visits, boiler and ventilation service, scale service, deep inspection of high-risk equipment | Contractor report, date, next due |
Calibration Log Template
Calibration compares an instrument to a known reference and records the difference. Use one line per check.
| Field | Example entry |
|---|---|
| Instrument ID and location | TH-014, cook kettle 2 probe |
| Reference used | Certified reference thermometer, ID and certificate date |
| Check date and method | Ice-point and boiling-point check, or comparison to reference |
| As-found reading and tolerance | Reads 0.4 °C high; tolerance ± 1.0 °C |
| Result | Pass / fail, adjusted yes or no |
| Next due date | Set by your written procedure |
| Done by and reviewed by | Initials and date for both |
How to Set Up an Equipment Calibration Program
- List every instrument that measures something your food safety plan depends on: thermometers and probes, pH meters, scales, data loggers, metal detectors and similar.
- Give each one a unique ID and label it with the last and next due dates.
- Choose a reference standard for each type and keep its certificate on file.
- Set a tolerance for each instrument based on the critical limit it monitors.
- Write the method and frequency into a procedure, as 21 CFR 117.165 expects.
- Run the checks, record the as-found reading before any adjustment, and have a second person review.
- Keep a spare calibrated instrument so a failed one can be swapped out immediately.
What to Do When a Calibration Check Fails
A failed check means readings taken since the last good check may be wrong. Tag the instrument out, replace or adjust it and re-verify, then review the monitoring records made with it since the last passing check. If product could have been released on bad readings, hold it, evaluate it and document a corrective action. Keep the failed check, the look-back and the decision together so the story is easy to follow in an audit.
Keeping Maintenance and Calibration Records Audit-Ready
Auditors usually sample: they pick a piece of equipment and ask for its last three records, or pick an instrument and ask when it was last checked and against what. Paper binders work until the sheet is missing or the initials are illegible. A digital record keeps the schedule, the result and the reviewer in one place. For how digital work instructions fit in, see our guide to digital SOPs and work instructions in food manufacturing.
In IONI, operational checks can be set up as scheduled calibration and verification tasks. Operators complete them in the To-Do app with a pass or fail, photos and notes, the log keeps who filled it in and who reviewed it, and a failed check can trigger an AI-drafted deviation and corrective action. IONI is not a CMMS, so work orders and spare-parts inventory stay in whatever maintenance system you use; it covers the checks and the records around them.
FAQ
What is a maintenance log in a food plant?
A record of preventive and corrective maintenance on equipment: the asset, the task, the date, who did it, the result and any follow-up.
How often should food plant equipment be calibrated?
It depends on the instrument, its use and its history. 21 CFR 117.165 requires the method and frequency to be set in your written procedures, so choose a frequency you can justify and then follow it.
What is the difference between calibration and verification?
Calibration compares an instrument to a reference and adjusts it if needed. Verification is a broader check that your preventive controls are working, and calibration of monitoring instruments is one of the verification activities.
Who should review calibration records?
Someone other than the person who did the check. Under 21 CFR 117.165 a preventive controls qualified individual, or someone under their oversight, reviews the records.
What happens if a thermometer fails calibration?
Take it out of service, replace or adjust it, and review the records made with it since the last passing check. Hold and evaluate any product that may have been affected.
Last updated: October 14, 2026
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