Guide · Food safety · UK
Every temperature record rests on the probe that made it. Checking accuracy takes ice, boiling water and minutes.
Every temperature record you keep - cooking, cooling, hot-holding, fridge checks - is only as trustworthy as the probe that produced it. A probe that reads two degrees low turns a genuinely safe kitchen into a paper trail of unsafe-looking numbers, and one that reads high can hide a real problem. Keeping probes accurate and evidenced is one of the cheapest, highest-leverage habits in food safety, and it is one an inspector can test on the spot.
Temperature is the control at the heart of most food safety systems, and the probe is the instrument that verifies it. If the probe drifts, every downstream record inherits the error, and your due-diligence evidence quietly becomes unreliable. That is why "check the probe" is not a nicety - it is the foundation the rest of your temperature discipline stands on. The good news is that verifying a probe takes minutes and needs nothing more exotic than ice and boiling water.
The method
You check a probe against two known temperatures that bracket the range you actually use - the freezing point of water and its boiling point. Between them they confirm the probe is accurate at both the cold and hot ends.
For the ice point, fill a container with crushed ice and a small amount of cold water so the ice does not float, stir it into a slurry, insert the probe without touching the sides or base, and let it settle for a few minutes - it should read 0C. For the boiling point, a rolling boil should read 100C, remembering that water boils slightly lower at altitude. The ice method is the safer and most reliable of the two for everyday checks. Keep the probe clear of the container walls in both, since touching them gives a false reading.
Adjust or replace
If the probe reads within about a degree of the reference, it is fine to use. If it is outside tolerance, the next step depends on the type. Bimetallic dial thermometers usually have an adjustment nut you can turn to bring them back to the reference point. Most digital catering probes cannot be user-calibrated - if a digital probe is out of tolerance and has no reset function, the correct action is to take it out of service and replace it, not to keep using it with a mental correction. A probe you cannot trust and cannot adjust has no place in the kitchen.
Check probes at sensible triggers: before first use, at a routine interval you set, after a probe has been dropped, and after it has swung between temperature extremes. Between uses, clean and disinfect the probe with a probe wipe so it does not itself become a cross-contamination route - and never let a probe touch bone or fat when measuring core temperature, as that skews the reading. These checks sit naturally alongside the daily temperature-control records EHOs expect and underpin tasks like cooling food safely at volume, where a trustworthy probe is the difference between control and guesswork.
Prove it
A calibrated probe with no record is only half the job. Keep a simple calibration log - date, which probe, the reading at each reference point, and any adjustment or replacement made. If a contractor calibrates for you, their record should identify the instrument and the correction applied. That log does two things: it demonstrates to an officer that your temperature records rest on a verified instrument, and it gives you a history that flags a probe starting to drift before it fails outright.
When an inspector arrives, a probe check is one of the quickest things they can do - they may test with their own calibrated reference, or ask to see yours and your log. A kitchen that can produce an accurate probe, a probe wipe, and a calibration record in one movement is signalling exactly the control that lifts confidence in management. It is a small routine that belongs in the same folder as the rest of the documents to have ready before an unannounced visit.
Questions
Check it against two known temperatures. For the ice point, make an ice slurry from crushed ice and a little water, stir, insert the probe without touching the container, and it should read 0C. For the boiling point, a rolling boil should read 100C at sea level. If the reading is outside about plus or minus one degree, recalibrate or replace the probe.
Set a routine interval, and always check before first use, after a probe has been dropped, and after it has been exposed to temperature extremes. Many kitchens do a documented ice-point check regularly as part of their food safety system.
A commonly used acceptable tolerance is plus or minus one degree Celsius. If the probe reads outside that against the reference points, it should be recalibrated where possible or replaced if it cannot be adjusted.
Most digital catering probes cannot be user-calibrated. If a digital probe reads out of tolerance and has no reset function, take it out of service and replace it. Do not keep using a probe you cannot trust by applying a mental correction.
Yes. Keep a simple log recording the date, which probe, the reading at each reference point, and any adjustment or replacement. It demonstrates to an inspector that your temperature records rest on a verified instrument and helps you spot a probe drifting before it fails.
Phoenix Duct Clean · by the numbers
Accurate probes and a certificated deep clean are two halves of the same demonstrable control. We deep-clean commercial kitchens to match your temperature discipline.