What is a temperature excursion?

A temperature excursion is any time a product, or the fridge, freezer, cold room, store or vehicle holding it, goes outside its required temperature range. For refrigerated medicines and vaccines that range is usually +2 to +8 °C; frozen food is usually held at −18 °C or below; blood products and laboratory samples have their own limits.

An excursion does not automatically mean the product is lost. What matters is how far the temperature went, for how long, and what the manufacturer's stability data allows. What every inspector and auditor will want to see is that you noticed it, assessed it, recorded it and fixed the cause. This article covers what counts, examples, why it matters and what to do. For the step-by-step response, see temperature excursions: what to do and record.

What counts as an excursion

An excursion is defined by the product, not the equipment. The range on the label or in the product's storage conditions is the limit that matters. A fridge that reads 8.5 °C for ten minutes during restocking and a freezer that warms to −15 °C for an hour are both excursions, even if neither product is harmed.

Common examples

• Refrigerated medicines stored above +8 °C, for example after a door is left ajar.
• Vaccines exposed to freezing temperatures, often from stock packed against the back wall of a fridge.
• Blood products or laboratory samples held outside their approved range.
• Ambient medicines exposed to heat in a store room or a vehicle during a heatwave.
• Frozen food that warms during a defrost cycle, a power cut or a long loading time.
• A delivery delayed in transit, so the load spends longer outside controlled storage than planned.

Excursions can be short spikes (a door left open, a busy restock) or long failures (a compressor fault, a power cut overnight). Going too cold matters as much as going too warm: freezing can destroy a vaccine without any visible sign.

Why excursions matter

Patient and food safety

A vaccine or medicine kept outside its range may lose potency, and nobody can tell by looking at it. In food, freezing slows bacterial growth but does not kill all pathogens; if a product warms above safe limits, they can multiply once it thaws.

Stock and money

A single fridge can hold vaccines, biologics, investigational medicinal products or specialist medicines that are costly and hard to replace. If you cannot show how long stock was out of range, you may have to quarantine or dispose of it. That means replacement costs, delays to patient treatment and supply disruption. In food, it means wasted stock and, at worst, a recall.

Compliance

Wholesale dealers work to Good Distribution Practice, vaccine holders to the Green Book, food businesses to their HACCP plan and, for many, BRCGS. Each expects storage conditions to be controlled and recorded, and deviations to be investigated with corrective and preventive action (CAPA). Missing records, a slow response or an unfinished investigation will raise questions at an inspection. Being able to prove control matters as much as having it.

Common causes

• Equipment failure: fridges, freezers, chillers and vehicle units degrade over time, and a fault can go unnoticed until the temperature is already out of range.
• Human error: doors left open, wrong thermostat settings, overloading, stock blocking airflow, or an alarm nobody responds to.
• Power interruptions: outages, surges or a backup that does not start.
• Environment: heatwaves, poor ventilation and inadequate air conditioning push units harder.
• Transport: delays, unmonitored vehicles and refrigeration units that fail on the road.

What to do when one happens

Your own procedure comes first, but the shape is the same in most sectors. Act on the product, then find the cause, then write it down.

1. Quarantine the stock at the right temperature and label it so nobody uses it.
2. Record the facts: the highest or lowest temperature reached, how long it lasted, which products were inside.
3. Get advice from the manufacturer, your pharmacist or your local immunisation team before using or discarding medicines and vaccines. Food teams follow their HACCP corrective actions.
4. Fix the cause and check the unit is holding its range before restocking.
5. Close the record with the decision, the corrective action and who signed it off.

Why manual checks miss excursions

Twice-daily checks give you two snapshots. A fault that starts after the evening check can run all night unseen, and a min/max thermometer tells you the extreme but not when or for how long. Without that history, an investigation is guesswork, and guesswork usually means disposing of stock that might have been fine. Manual logs also bring missed readings and transcription errors.

Automated wireless monitoring logs every unit around the clock and sends alarms that reach a person by SMS, phone call, email or app, escalating until someone acknowledges. The full temperature history is there for the assessment, with the alarm, the acknowledgement and the corrective action in one record. JTF monitors units at 350+ UK sites this way through the Sematics platform.

Preventing the next one

• Monitor continuously with sensors placed where the risk is, ideally informed by a mapping study.
• Calibrate monitoring sensors at the interval your procedure sets, so the readings stand up. See calibration.
• Maintain equipment and act on early warnings, such as a unit that runs warmer each week.
• Train staff so everyone knows what the alarm means and what to do at 2am.
• Review excursions together, so repeat causes are fixed rather than recorded again.