The hidden signals behind temperature excursions in healthcare and life sciences
A medical refrigerator rarely moves from normal operation to complete failure without warning. Long before an alarm sounds, there may be subtle changes: the compressor runs for longer, temperatures recover more slowly after stock handling, doors are opened more frequently, airflow becomes restricted or the surrounding environment places greater demand on the unit.
For hospitals, pharmacies, laboratories, clinical-trial sites and pharmaceutical facilities, these changes matter. Refrigerators and freezers may contain vaccines, medicines, biological samples, reagents or other products whose integrity depends on controlled conditions. When performance deteriorates, the consequences can include quarantine, investigation, delayed treatment, disrupted research and costly product loss.
Temperature remains the fundamental measurement. However, it may show the final symptom rather than the conditions that allowed the problem to develop. Looking at what happens before an excursion can help teams respond earlier.
Temperature may be the final warning
A temperature excursion occurs when a controlled storage environment moves outside its established limits. The immediate investigation must determine when the excursion began, the highest and lowest temperatures reached, how long it continued and which products were affected.
The NHS Specialist Pharmacy Service guidance on managing temperature excursions recommends collecting precisely this information. It also notes that continuous data loggers provide a more detailed account than minimum/maximum recorders, supporting better-informed decisions about affected medicines.
Rob Lelliott is UK Sales Manager for Life Sciences at Kelsius. Kelsius provides automated temperature monitoring solutions for laboratories, private healthcare groups, NHS trusts, pharmaceutical companies, as well other organisations involved in developing and providing healthcare. According to Rob, “Gathering data will help to establish when an excursion began and the event’s severity, but it doesn’t always establish the cause.” He continues, “A unit may have been losing resilience for days or weeks before the temperature finally crossed an alarm threshold.”
In healthcare, an alarm should never be viewed as the start of the incident. It is often the point at which an underlying issue becomes visible. Rob adds, “The real opportunity is to identify deteriorating performance early enough to protect the products before an excursion occurs.”
1. The compressor is working harder
The compressor helps remove heat from the storage chamber. Its operating pattern varies with equipment type, set point, ambient conditions and day-to-day use. Longer or more frequent cycles may follow repeated door openings, a large stock load, restricted ventilation, high room temperature, icing or declining component efficiency.
A temporary increase in activity is not necessarily a fault. A sustained departure from the unit’s established pattern, particularly when combined with slower temperature recovery, can provide valuable context for maintenance teams.
The World Health Organization’s temperature-monitoring guidance for vaccine cold-chain equipment identifies growing potential to monitor parameters such as compressor function, voltage input and humidity alongside temperature. WHO links these wider data to deeper performance insight, remote failure analysis and, ultimately, more predictive responses.
2. Power events can influence refrigeration
Medical refrigeration depends on reliable electrical power for compressors, fans, controllers, communications and alarms. A complete outage is obvious, but shorter interruptions or voltage instability may be less visible. A display or internal light can remain active even when cooling performance has been affected.
Recording power events alongside temperature history can help establish whether an electrical disturbance preceded instability. According to Rob Lelliott, this is particularly important for unattended locations, facilities with backup power and sites where stored products have high clinical or financial value. “Temperature data tells the team what happened inside the fridge. When it is combined with information such as power loss, door activity and alarm history, it becomes much easier to understand why it happened and what action may prevent a repeat.”
3. Door activity and recovery time reveal operational strain
Each door opening allows warmer air to enter. In a busy pharmacy, ward, laboratory or dispensing area, repeated access may create a significant cumulative heat load. Problems become more likely when doors are left open, seals are damaged or staff need to search through poorly organised stock.
A short rise after stock handling may be expected. Recovery time is often more informative: how quickly does the chamber return to its normal range, and is that response changing over time?
If an equivalent stock movement once produced a quick recovery but now takes much longer, the unit may be under additional strain. Possible causes include overloading, airflow obstruction, high ambient temperature, frost accumulation, maintenance issues or reduced cooling efficiency.
NHS guidance on establishing alerts for temperature-monitoring systems recommends considering alarm points that provide warning before an excursion occurs. It also advises keeping alarm delays as short as practical while allowing for acceptable transient changes, such as those caused by opening a refrigerator door.
4. Airflow, loading and sensor position matter
An acceptable reading at one point does not prove that conditions are uniform throughout a cabinet, cold room or freezer. Chilled air must circulate around the stored load. Overfilled shelves, blocked vents and unsuitable product placement can create localised warm or cold areas.
The NHS Specialist Pharmacy Service’s sensor guidance distinguishes between air sensors, which can provide early warning of environmental change, and load sensors, which can indicate how the stored medicine itself may be responding. It recommends considering both for refrigerators and freezers because they answer different questions during an excursion.
For larger or higher-risk storage environments, temperature mapping can identify vulnerable locations and inform the placement of permanent sensors. European Commission Good Distribution Practice guidelines for medicinal products similarly require initial temperature mapping of storage areas under representative conditions, followed by risk-based repetition.
From reactive alarms to earlier intervention
A conventional alarm answers an essential question: has the temperature crossed its limit? Trend-based monitoring can ask an earlier one: are conditions changing in a way that could cause an excursion later?
Potential warning patterns include progressively slower recovery, temperatures remaining closer to a limit, unusual compressor activity, repeated fluctuations during particular shifts, power interruptions, rising ambient temperature or increasingly frequent maintenance requirements.
Rob Lelliott notes, “The objective is not to overwhelm healthcare teams with more data. It is to make the important changes visible and actionable. Monitoring should help the right person understand the risk quickly, document the response and intervene before product integrity is compromised.”
Building a more preventive monitoring approach
No single parameter can predict every failure, and not every storage location requires the same monitoring strategy. The correct approach depends on the products, equipment, regulatory obligations, operating environment and consequences of loss.
Organisations can strengthen their approach by asking:
- Is performance stable across days, shifts and seasons?
- Does the unit recover normally after access or stock loading?
- Are airflow and sensor positions appropriate for the stored load?
- Are door, power and alarm events recorded with the temperature history?
- Are alerts early enough, clearly escalated and actionable out of hours?
- Are trends actively reviewed rather than simply retained for compliance?
Looking beyond the temperature alarm
Temperature will remain fundamental to healthcare and life-sciences storage. It is the measurement used to establish whether defined conditions have been maintained and to support decisions when an excursion occurs.
But a door may have been opening more frequently, airflow may have changed, the compressor may have been working harder, or the equipment may have been taking progressively longer to recover. By the time a threshold is crossed, the underlying problem may already have been developing for some time.
Understanding these preceding signals can help organisations move from simply reacting to excursions towards recognising changing conditions earlier. That creates more time to investigate, document and intervene, helping protect medicines, vaccines, samples and other temperature-sensitive materials before an alarm becomes a clinical or operational crisis.
For advice on automated temperature and humidity monitoring, or advice on temperature mapping, contact Kelsius:
Tel. +44 (0)2045 799 048, email sales@kelsius.com
