Should Every Temperature Excursion Should Be Investigated?

Occasionally, a fridge, freezer, or storage area may record a temperature outside its recommended range. This is known as a temperature excursion.

But there’s a difference between a short temperature excursion caused by an open door or one caused by an overnight power failure. So, when is an excursion something that needs investigating?

Correct storage temperatures are essential in the handling of medicines. Many medicines, vaccines and healthcare products are temperature-sensitive. If they spend an amount of time at the wrong temperature they become ineffective.

What Is a Temperature Excursion?

A temperature excursion occurs whenever a medicine, vaccine, or healthcare product is exposed to temperatures outside its approved storage conditions.

For example, most pharmacy refrigerators are designed to maintain temperatures between 2°C and 8°C. If temperatures rise above 8°C or fall below 2°C, even for a short period, an excursion has occurred.

Not every temperature excursion means medicines need to be discarded. And there is no single source that says whether an excursion is a problem or not.

The important question is whether the quality, safety, or effectiveness of the affected products may have been compromised.

The most useful source is probably the NHS Specialist Pharmacy Service (SPS) guidance on managing temperature excursions.

It effectively provides a framework for assessing incidents.

Why Temperature Excursions Can Happen

Common temperature deviation reasons include:

• Environmental factors
• Equipment faults
• Fridge doors left open
• Incorrect thermostat settings
• Overloaded refrigeration units
• Poor airflow within storage equipment
• Moving stock between locations
• Transport and delivery issues

Some excursions have little impact. Others can affect a product’s stability, potency, and suitability for patient use to the extent the product needs discarding.

Why Temperature Excursions Matter

Many medicines are sensitive to temperature changes.

Vaccines are particularly vulnerable. Biological medicines, insulin products, and specialist pharmaceuticals may also be affected by temperature fluctuations.

In critical medications like insulin, EpiPens, or inhalers, excursions can lead to dangerous, life-threatening failures.

Because temperature-related damage is not always visible, you cannot rely on visual inspections alone. Decisions must be based on documented evidence in line with manufacturer guidance.

Every Temperature Excursion Should Be Investigated

Guidance from the NHS Specialist Pharmacy Service (SPS) is that every temperature excursion should be assessed and documented.

The purpose is not necessarily to discard stock. The aim is to determine whether the affected medicines are still suitable for use.

When an excursion occurs, SPS guidance suggests you should establish:

• The highest and lowest temperatures reached
• How long the excursion lasted
• Which products were affected
• Whether the products remained within acceptable stability limits
• The likely cause of the incident
• What corrective action has been taken

If you don’t know the exact duration or temperature range, use a worst-case assessment when making decisions.

This is one reason many healthcare organisations are moving away from manual temperature logs and adopting continuous monitoring systems. An automated monitoring solution can provide precise information about when the excursion occurred, how severe it was, and exactly how long it lasted.

Factors That Influence Risk

How Far Outside the Range Did the Temperature Move?

A small excursion may present little risk, while larger temperature changes are more likely to affect products.

If a pharmaceutical fridge’s temperature raises to:

• 2°C for a few minutes vs
• 10°C for several hours vs
• 20°C overnight

Each situation carries a different level of concern.

How Long Did the Excursion Last?

Duration is as important as the temperature itself.

A brief spike might have little impact if conditions quickly return to normal.

Longer excursions create greater uncertainty and increase the risk of product degradation.

Which Products Were Affected?

Some products can tolerate limited temperature deviations. Others require strict temperature control throughout storage.

Vaccines, biological medicines, blood products, and specialist pharmaceuticals often require closer assessment following an excursion.

This is where you should always look for manufacturer guidance when assessing affected stock.

Did Temperatures Fall Below Recommended Levels?

While elevated temperatures often receive the most attention, low temperatures can be just as problematic.

Vaccines and certain medicines can be permanently damaged if frozen, even if temperatures later return to the correct range.

Any indication that products may have frozen should be investigated thoroughly.

Example:

Imagine a pharmacy vaccine fridge is operating normally when staff leave at 6pm.

The fridge contains:

• Influenza vaccines
• Travel vaccines
• Insulin products
• Temperature-sensitive biological medicines

At 8am the following morning, a monitoring system reports that temperatures began rising at 11:30pm following a power interruption. The highest recorded temperature was 15°C, and the fridge remained above 8°C for six hours before power was restored.

You should immediately quarantine the affected stock and clearly identify it as awaiting assessment.

Because the monitoring system has recorded the entire event, you can determine:

• When the excursion started
• How long products were exposed
• The highest temperature reached
• When temperatures returned to the acceptable range

Then consult manufacturer guidance or specialist medicines information services to determine whether the affected products remain suitable for use.

Without continuous monitoring, staff may arrive the next morning and see a temperature with a high reading of 15°C. While this appears acceptable, it provides no indication of what happened overnight. Temperatures may have remained stable throughout the night, or they may have reached 15°C for several hours before cooling again.

This type of information makes investigations more difficult.

Common Excursions That Need Careful Assessment

While every excursion should be reviewed, some situations almost always need detailed investigation.

Environmental Factors

The location of the fridge or ambient storage area can influence temperature stability. Nearby heat sources, direct sunlight, poor ventilation, restricted airflow, seasonal temperature changes or placement in a busy area where doors are frequently opened can all contribute to fluctuations. The surrounding environment should be reviewed as part of the investigation to determine whether external conditions may have caused or worsened the excursion.

Fridge Failure

If your equipment stops operating, temperatures may remain outside the acceptable range for several hours before the issue is discovered.

Power Outages

Power interruptions can quickly affect refrigeration and should be assessed using the temperature data that’s available.

Extended Door Openings

Doors left open accidentally can cause prolonged temperature increases that may affect stored products.

Overstocking

Overstocking a fridge can restrict airflow and prevent cold air from circulating evenly around the stored products. This can create warm spots, slow temperature recovery after the door has been opened, and increase the risk of temperature excursions. Stock should be arranged to allow adequate space between items and should not block vents, fans or temperature probes.

Repeated Temperature Excursions

Recurring problems can be caused by equipment deterioration, poor maintenance, incorrect loading practices, or inadequate ventilation.

Evidence of Freezing

Any indication that medicines or vaccines may have frozen should be treated seriously. It’s vital when dealing with vaccines and biological products.

Not Every Excursion Results in Stock Loss

Many medicines can tolerate limited temperature excursions without affecting quality. The outcome depends on several factors, including the medicine involved, the temperatures reached and the duration of exposure.

Some medicines stored at room temperature can tolerate short-term exposure above their recommended storage conditions. Refrigerated medicines, vaccines, and biological products are often more sensitive to temperature fluctuations.

This is why documentation is so important. Decisions should be based on evidence rather than assumptions.

What Should You Do When an Excursion Occurs?

The priority is protecting potentially affected stock.

Products should be isolated from usable stock until an assessment has been completed.

Gather data, including:

• Maximum and minimum temperatures recorded
• Duration of the excursion
• Date and time of occurrence
• Products affected
• Potential cause
• Corrective actions taken

Check manufacturer guidance on storage to determine whether stock is tolerant or must be destroyed.

Why Digital Monitoring Supports Compliance

One of the biggest limitations of manual temperature logs is that they only provide a snapshot of conditions at specific points during the day.

A fridge could experience a significant overnight excursion and still appear compliant when checked the following morning.

Environment monitoring systems provide a more complete picture by recording temperatures around the clock, including:

• Continuous temperature recording
• Automated alerts
• Historical trend analysis
• Accurate excursion duration data
• Downloadable reports

These systems mean you can respond more quickly to problems. You can also provide stronger evidence during audits and inspections.

Preventing Future Temperature Excursions

While not every incident can be avoided, some excursions are preventable.

Regular equipment servicing, real-time temperature monitoring, staff training and routinely reviewing temperature records all play a part in reducing the effect of temperature changes. Also look at the proper loading of products and making sure alarms are working.

Final Thoughts

While not every excursion results in stock becoming unusable, every incident should be assessed and documented. This is the NHS guidance.

The effects of an excursion depends on how far temperatures moved outside the recommended range, how long the excursion lasted, and which products were affected.

Having accurate temperature data is critical. It gives you the information you need to investigate incidents properly, it supports compliance requirements, and protects valuable medicines and vaccines.

Modern storage and monitoring processes make it easier to identify and assess temperature excursions accurately is an increasingly important part of better patient care.