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GMP qualification guides

Thermal requalification of chambers, autoclaves and temperature-controlled environments

30 August 20266 min read

In breve

Thermal requalification (thermal mapping) periodically verifies that climatic chambers, autoclaves, refrigerators and GMP warehouses maintain temperature and uniformity within the limits, using networks of calibrated probes. It studies heat distribution (empty/loaded environment) and, for sterilization, penetration into the load. It is a risk-based periodic PQ activity.

Why temperature must be requalified

Temperature-controlled environments and equipment safeguard product quality: a stability chamber out of specification, an autoclave with cold spots, a warehouse with thermal stratification can compromise batches or studies. The initial qualification (OQ/PQ) demonstrates that the equipment works; the requalification demonstrates that it continues to do so over time.

Distribution and penetration

Two distinct studies, often confused:

  • Temperature distribution: maps the temperature throughout the volume, typically empty and loaded, to identify hot and cold spots and to verify uniformity.
  • Heat penetration: relevant for sterilization processes, it measures the temperature inside the load to demonstrate that even the most unfavorable point reaches the required conditions (for the autoclave, the link with F0).

How it is performed

The typical method:

  1. Definition of the protocol and of the acceptance criteria (limits, uniformity, worst case).
  2. Positioning of the probes according to a layout that covers the volume and the critical points, in a number adequate to the dimensions.
  3. Execution over representative cycles/conditions, often repeated (for sterilization, three compliant cycles).
  4. Data analysis and comparison with the criteria.
  5. Report and approval, with management of any deviations.

The probes and data loggers must be calibrated with traceability guaranteed through ACCREDIA-accredited laboratories: the mapping is worth as much as the calibration of the instruments that perform it.

How often to redo it

The frequency is risk-based and must be justified: the criticality of the environment, the historical stability and any modification (which activates change control) all have a bearing. Many sites adopt an annual periodicity for the most critical environments, but the number is not a dogma: it is a documented choice.

Domande frequenti

What is thermal requalification?

It is the periodic verification that a temperature-controlled environment or piece of equipment (climatic chamber, autoclave, refrigerator, GMP warehouse) maintains temperature and uniformity within the established limits. It is performed with networks of calibrated probes and studies heat distribution and, for sterilization, penetration into the load.

What is the difference between heat distribution and penetration?

Distribution maps the temperature in the volume of the equipment (empty and loaded) to verify its uniformity and identify hot/cold spots. Penetration measures the temperature inside the load and is typical of sterilization processes, where it is necessary to demonstrate that even the most unfavorable point reaches the required conditions.

How often must thermal requalification be done?

The frequency is risk-based and must be justified according to the criticality of the environment, the historical stability and any modifications. For the most critical environments an annual periodicity is common, but it is not a fixed obligation: the periodicity is a documented decision.

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