UKAS accredited calibration laboratory No. 10723

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For pathology and medical laboratory quality managers

What ISO 15189 requires of temperature

ISO 15189:2022 expects a medical laboratory to monitor, control and record the environmental conditions that affect its results, and to calibrate the equipment that measures them with traceability to national standards. In a UKAS assessment that means every fridge, freezer, incubator and room that matters has a defined range, calibrated monitoring, alarms set with the sensor's uncertainty in mind, and a record of what happened when it went out of range.

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Updated 19 October 2026Reviewed by Jake Farrow, Managing Director

At a glance

What it asks

The rule in pictures

Alarm limits inside the range, and who expects what

A sensor reading of +5.9 °C on a 2 to 6 °C fridge isn't proof the fridge is in range if the sensor's uncertainty is ±0.3 °C. Setting alarms inside the limits takes that into account.

Blood bank fridge: guard bands for uncertaintyIllustrative
  • Required range for red cells, 2 to 6 °C
  • Alarm limits set inside it as a guard band for measurement uncertainty

Example limits only. The width of the guard band comes from the uncertainty on your sensor's calibration certificate and your own decision rule.

What each regime looks for on temperature
ISO 15189BSQRHTA
Monitoring and records✓✓✓
Calibrated, traceable sensors✓✓✓
Alarms acted on and recorded✓✓✓
Uncertainty taken into account✓··

A simplified view for blood and tissue storage in a lab. Check each regime's own text for your scope.

ISO 15189 6.3 and 6.6.2

Facilities and environmental conditions

What it says

The laboratory makes sure its facilities and environmental conditions are suitable for its activities and don't adversely affect the validity of results. It specifies, monitors and records the environmental conditions its activities need, including at sites away from the main laboratory and for point-of-care testing (6.3.1). Storage keeps samples, reagents, consumables and records intact (6.3.3), and reagents are stored to the manufacturer's specification, with conditions monitored where relevant (6.6.2). Safety facilities are checked regularly to show they work (6.3.2 d)); the standard's own examples include alarm systems for cold rooms and walk-in freezers, which supports routine alarm tests.

What it means on site

Assessors look past the analysers to the edges: the reagent fridge in the corridor, the sample store in the basement, the room temperature in the lab where kits are kept at 'room temperature'. If a range is on the kit insert, someone will ask how you know you held it.

How to evidence it

  • A list of monitored storage and rooms, each with its required range and where that range comes from
  • Temperature records for each one, with gaps explained
  • Who reviews the records, how often, and the evidence they did

ISO 15189 6.4

Equipment: identified, maintained and shown to work

What it says

Equipment that can influence results is selected and shown to be fit for purpose before use, uniquely identified, maintained and kept in safe working order, with records of performance, maintenance and any damage, malfunction or repair. Refrigerators, freezers and incubators that hold samples and reagents are part of this. Before equipment goes into service, or back into service, it is checked against acceptance criteria (6.4.3); that check can rest on the calibration certificate, which is why you review and approve each certificate yourself. Equipment that is defective or outside requirements is taken out of service and labelled, and its effect on earlier work is examined (6.4.5 c)). Calibration certificates are kept in the equipment record (6.4.7 j)).

What it means on site

A freezer replaced after a failure often keeps the old asset number in the records but not the new verification. The assessor will want to see that the unit in front of them was checked before it held samples.

How to evidence it

  • An equipment record for each fridge, freezer and incubator: identifier, location, acceptance check
  • Maintenance and service records, and what was done after each failure
  • Evidence the unit holds its range in use, such as a temperature study or performance check

ISO 15189 6.5

Calibration and metrological traceability

What it says

Measuring equipment, including the temperature sensors that monitor storage, is calibrated to a defined programme where it affects results. Calibration establishes metrological traceability to national or international standards, and the laboratory takes the reported measurement uncertainty into account in using the results. UKAS policy (TPS 41, applying ILAC P10) expects traceability through a national measurement institute or an accredited calibration laboratory, or otherwise demonstrated. Calibration by a competent laboratory gives traceability, and a laboratory meeting ISO/IEC 17025 counts as competent (6.5.3 b), Note 1). That is why many ISO 15189 laboratories ask for UKAS accredited calibration, while traceable calibration remains a valid route where you can show it.

What it means on site

The certificate is often on file but nobody has read the uncertainty column. If the uncertainty is close to the gap between your reading and the limit, you can't say for certain the fridge was in range.

How to evidence it

  • A calibration certificate for each monitoring sensor, in date, with traceability and uncertainty stated
  • Your calibration programme: which sensors, how often, by whom
  • A link between each certificate and the sensor installed in each unit today

UKAS LAB 48

Uncertainty and guard bands: setting alarm limits

What it says

UKAS LAB 48 explains how a statement that something is in or out of specification depends on a decision rule, which takes the measurement uncertainty into account, often by setting a guard band inside the limit. The same reasoning applies to alarm limits: if the alarm sits exactly on the edge of the required range, readings inside the alarm can still mean the true temperature is outside it.

What it means on site

Alarm limits set exactly at 2 and 6 °C, with no account of uncertainty, is a common gap. Moving them in by a guard band and writing down why answers the question before it's asked.

How to evidence it

  • The decision rule you use for temperature: how uncertainty sets the guard band
  • Alarm limits for each unit, with the reasoning written down
  • Calibration uncertainty for each sensor, matched to its alarm limits

ISO 15189 7.5, 8.7 and 8.4

Nonconformities, corrective action and records

What it says

When something goes outside requirements, the laboratory reacts to control and correct it, assesses the consequences for results and samples (including those already reported), investigates the cause and takes corrective action proportionate to its effect. Nonconforming work explicitly includes equipment or environmental conditions outside specified limits (7.5), so a fridge running out of range is one. Records are kept to show what happened and what was done, controlled so they can be retrieved and protected from change. The standard sets no retention period: it asks that retention times are specified, and they can be chosen on risk (8.4.3); RCPath's guidance supplies the periods UK laboratories use.

What it means on site

The alarm was answered, the door was shut, but nobody recorded whether the samples or reagents were affected. Without that assessment the event isn't closed in the assessor's eyes.

How to evidence it

  • A nonconformity record for each out-of-range event: start, peak, duration, response
  • The assessment of impact on samples, reagents and reported results
  • Root cause and corrective action, signed off
  • Trend review: repeat events on the same unit and what changed

ISO 15189 7.2.5 and 7.6

Sample transport and the systems that hold the data

What it says

The laboratory gives instructions for keeping the required temperature while samples are transported (7.2.5 a) 3)). Systems that store or report data, such as a monitoring platform, are validated by the supplier and verified by the laboratory before use (7.6.3 a)), with plans for when they are down (7.6.4). Where an information system is managed off site or by an external provider, the laboratory makes sure the provider meets the standard's requirements (7.6.5). That is the laboratory's duty, supported by the supplier's evidence.

What it means on site

A hosted monitoring platform is often treated as the supplier's problem. The assessor will ask how you verified it before use, what you do when it is down, and how you know the provider meets the standard.

How to evidence it

  • Transport instructions with the temperature to keep and how it is checked
  • The supplier's validation evidence and your own verification before use
  • A downtime plan for the monitoring system
  • How you assure an off-site or external provider, with the evidence you hold

In the inspector's words

Questions to be ready for

The kind of questions an inspector, assessor or auditor puts. If you can answer each with a record, you're ready.

  1. “Show me the temperature record for this fridge for the last three months.”
  2. “Where does this range come from, and why is the alarm set there?”
  3. “What is the uncertainty on this sensor's calibration, and how have you allowed for it?”
  4. “Is this the sensor on this certificate? Who calibrated it, and are they accredited?”
  5. “Talk me through the last time this freezer alarmed. What happened to the samples?”
  6. “Who reviews these records, and where would I see that they did?”

Where JTF fits

Where JTF fits

We monitor fridges, freezers, incubators and rooms in 25 NHS trusts, health boards and pathology networks, and provide calibration for every sensor we supply: traceable to national standards as standard, or UKAS accredited where you need it (temperature in our own UKAS accredited calibration laboratory No. 10723; other parameters through accredited partners). Each certificate, with its uncertainty, sits against the sensor in Sematics, and we can help you set alarm limits that allow for it. Every alarm, response and sign-off is on one record your assessor can review. At Wye Valley NHS Trust, the blood transfusion team shows assessors and inspectors the Sematics record at every visit.

Checklist

ISO 15189 temperature checklist

Monitoring, calibration, uncertainty and records, with the clauses, on one page.

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The 20-minute compliance check

See your own gaps, in writing

A free call with one of our specialists, then a branded report of what an inspector would find, yours to keep. This is an example.

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Example reportExample report: ISO 15189An NHS pathology lab (fictional)Download the PDF
Example report: ISO 15189
Page 1 of the example report: iso 15189Page 2 of the example report: iso 15189Page 3 of the example report: iso 15189

Related

Keep reading

Questions

Common questions

Does ISO 15189 require continuous monitoring?

It requires conditions to be monitored, controlled and recorded where they can affect results (6.3), and doesn't prescribe the method. In practice, out-of-hours alarms and a continuous record are how most labs show control overnight and at weekends.

Do our temperature sensors need UKAS-accredited calibration?

The standard asks for metrological traceability (6.5). Calibration by a competent laboratory gives it, and a laboratory meeting ISO/IEC 17025 counts as competent (6.5.3 b), Note 1), so UKAS treats an accredited calibration certificate as the usual way to show it and many labs ask for UKAS. Traceable calibration by another route is possible, but you then need to demonstrate the traceability yourself.

How should we set alarm limits?

Inside the required range, by a guard band that reflects the sensor's calibration uncertainty and how quickly the unit drifts. Write down the reasoning; UKAS LAB 48 sets out how decision rules work.

What changed for temperature in the 2022 edition?

The requirements for facilities, equipment and calibration sit in clause 6, and the 2022 edition puts more weight on risk. The temperature expectations themselves are much the same; see the standard for the detail.

Does a temperature excursion have to be a nonconformity?

If it takes storage outside the required conditions, treat it as one: control it, assess the effect on samples and results, find the cause and record the corrective action (7.5 for the effect on samples and results, 8.7 for corrective action).

Does ISO 15189 say how long to keep temperature records?

No. It asks you to specify retention times and lets you set them on risk (8.4.3). RCPath's guidance supplies the periods most UK laboratories use, for example 15 years for blood bank fridge charts.

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Sources

  1. ISO 15189:2022 Medical laboratories: requirements for quality and competence
  2. UKAS: Medical laboratory accreditation (ISO 15189)
  3. UKAS TPS 41: UKAS Policy on Metrological Traceability
  4. UKAS LAB 48: Decision rules and statements of conformity
  5. The Blood Safety and Quality Regulations 2005
  6. Human Tissue Authority: codes of practice and standards (including the post-mortem sector)
  7. JTF guide: Measurement uncertainty in medical laboratory temperature monitoring

This summary isn't official guidance. The source documents are what an inspector works from.

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