The probe thermometer question inspectors love to ask

EHO Story 📩

There are certain questions EHOs and auditors ask during inspections that instantly reveal how well a kitchen understands its food safety systems.

One of those questions is about probe thermometer calibration.

It usually sounds simple enough.

“How do you check your digital probe thermometer is giving accurate readings?”

And very often the answer comes back confidently.

“Oh, I just pop it in the freezer for a few minutes.”

Then comes the awkward pause.

Because in that moment you realise they do not actually know how to check it properly.

I have heard this many times over the years, both when working for local authorities and when auditing kitchens independently.

The paperwork often tells the same story.

Every single entry recorded as 0°C.

Perfectly neat.

Perfectly consistent.

And almost certainly not correct.

Because the purpose of a probe calibration check is not to produce a perfect number.

It is to check that the thermometer is accurate.

Freezers are not reliable for this. They can sit anywhere between -12°C and -22°C depending on the unit and how often the door is opened. So putting a probe in the freezer for a few minutes does not actually tell you anything useful about accuracy.

Which means the check, and the records that follow, are meaningless.

Food Safety Tip ✅

If you are checking your probe thermometer using the ice water method, here’s what to do:

✔️ Mix equal parts ice and water in a container. If any ice floats off the bottom, pour away some water or add more ice.

✔️ Place the probe into the container and stir gently, making sure the probe does not touch the bottom or sides.

✔️ Allow the temperature to stabilise.

The reading should fall between -1°C and 1°C.

If it does, the probe is working correctly.

**ETI has a really helpful video showing the ice water method, which you can watch here.**

When recording the check, write down the actual reading, not just “0°C”.

For example:

✔️ +0.4°C

✔️ -0.3°C

Recording the real reading shows the check has genuinely been carried out.

The Serious Lesson

Calibration checks are not paperwork exercises.

They exist to confirm that the equipment you rely on to keep food safe is actually working properly.

EHOs and auditors ask about probe checks because they want to understand whether the system is genuinely being followed, or whether records are simply being filled in.

A quick freezer check and a neat “0°C” written in the log might look good on paper.

But a proper ice water test, and an honest reading in the record book, tells a very different story.

And it is that story inspectors are really looking for.