Executive summary
526M tonnes
of food lost yearly to inadequate refrigeration, 12% of global production, per FAO/IIR
Key conclusions
- A scheduled spot check records only the temperature at the moment someone looked. It shows nothing about a four-hour excursion between checks.
- WHO's vaccine cold-chain guidance recommends continuous monitoring because it shows when an excursion started, how long it lasted and whether the product is still viable.
- A defensible record needs continuous logging close to the product, a threshold based on cumulative time outside the range, and an escalation path that quarantines product instead of discarding it automatically.
A refrigerated shipment can pass every scheduled temperature check on its route and still spend four hours outside its allowed range between two checks. Each check records the temperature at the moment someone looked. It shows nothing about the period in between, which is when excursions happen.
A 2021 report from the UN Food and Agriculture Organization and the International Institute of Refrigeration shows the scale of the cost. It puts the food lost each year to inadequate refrigeration at 526 million tonnes, 12 percent of global food production. Not all of that loss comes from monitoring failures. Part of it does: the product was compromised in transit or storage, and nobody knew until it was opened.
Spot checks miss excursions because cold chain failures are sudden
A periodic check assumes that temperature drifts slowly and predictably between readings. Reefer units and cold rooms do not fail that way. A door left open at a transfer point, a compressor cutting out or a pallet blocking the airflow each causes an excursion within a short window. A fixed check schedule is not designed to catch these windows.
The World Health Organization's vaccine cold chain guidance makes the same point from the regulatory side. WHO specifies a storage range of 2°C to 8°C for vaccines. It recommends continuous monitoring because it is the only method that shows when an excursion started, how long it lasted and whether the product is still viable. Once an excursion has passed, a spot check cannot answer any of these three questions. It can only show that the temperature was within range the last time someone checked.
Continuous monitoring records what spot checks miss
| Scheduled spot check | Continuous sensor monitoring | |
|---|---|---|
| What it records | The temperature at the moment of the check | The full temperature history across the journey |
| A short excursion between checks | Caught only if the check happens to land inside it | Caught every time; the record has no gap |
| Basis for a release or discard decision | An assumption about what happened in between | The measured duration and severity of the actual excursion |
| What it can show an auditor | A logbook that looks clean because it wasn't looking at the right minute | A time-stamped record produced on request |
A defensible cold chain record needs four things
- Continuous logging at the product or pallet, as well as in the vehicle or room. The most important reading is the one taken closest to the product that can spoil.
- An excursion threshold based on cumulative time outside the range. WHO's own vaccine guidance discards a dose only when cumulative time outside the approved range passes a defined limit, checked against a vaccine vial monitor.
- An escalation path that does not default to automatic discard. WHO guidance states clearly that a suspected excursion should be labelled and quarantined until a qualified person with product-specific knowledge makes the decision.
- Records kept long enough to answer a customer, an auditor or a recall investigation. A HACCP (Hazard Analysis and Critical Control Points) or FSSC 22000 audit already sets this standard of evidence, and a paper log rarely meets it fully.
All of this requires only a few connected sensors and a clear excursion rule, applied to a process most operators already run. That is why it is usually the fastest-paying part of a logistics digitalisation programme.
