SOP: Thermal Mapping and Requalification Program

This is a ready-to-use SOP for running a thermal mapping program across storage and processing equipment. Replace every <<FILL: ...>> placeholder with your specifics, set your document numbers and dates, and route it through document control. A worked filled specimen follows. Verify each cited standard against the current source before you rely on it.

Document control header

1. Purpose

This procedure defines how <<FILL: COMPANY NAME>> plans, executes, and maintains temperature mapping studies so that every position a product can occupy inside a controlled unit is proven to hold its rated condition. It sets the sensor-count logic, study design, acceptance basis, and requalification triggers, so mapping evidence supports storage and processing claims rather than assumption.

2. Scope

This procedure applies to temperature-controlled and thermally-critical equipment at the sites in the header, including stability chambers, refrigerators and freezers (including ultra-low), walk-in cold rooms, ambient and controlled warehouses, and moist-heat and dry-heat sterilizers and ovens. It covers empty, loaded, door-open, and, where required, power-loss studies, and the routine requalification of qualified units. Cycle development for sterilization is governed separately under <<FILL: SOP-ID for sterilization validation>>.

3. Responsibilities

4. Definitions

• Usable volume: the space product may occupy, excluding manufacturer-reserved clearance near walls, ceilings, fans, and coils.
• Hot spot / cold spot: the mapped positions that most often hold the warmest and coldest readings; they define the real operating envelope.
• Mean kinetic temperature (MKT): a single temperature that imposes the same thermal stress as the varying real conditions; used to judge controlled-room-temperature storage and excursions.
• Measurement uncertainty: the combined uncertainty of the logger plus its calibration, factored against the acceptance band.

5. Procedure

5.1 Plan the study

1. Define the unit (asset ID), rated condition, allowable excursion, and usable volume from the URS or equipment specification.
2. Select the studies required using the risk of the stored material and the equipment class (section 5.2).
3. Set the sensor count and placement by risk (section 5.3), not by copying a template.

5.2 Select the studies

5.3 Set sensor count and placement

1. Use the baseline as a floor, not a rule: around 9 sensors for a small reach-in, 15 or more for a walk-in, 20 or more for a warehouse. Justify the number in the protocol.
2. Include, regardless of count: the 8 geometric corners of the usable volume, the center, a sensor adjacent to the control probe, the door zone, the supply-air and return zones, and any internal heat or cold source.
3. Place a sensor next to the routine monitoring / building-management probe to qualify it against mapped reality.
4. Mark the usable volume physically (load lines) and place no sensors in unqualified dead zones.

5.4 Instrument and calibrate

1. Use independent, battery-powered data loggers, not the unit’s control sensor, as the mapping evidence.
2. Calibrate every logger against a standard traceable to a national metrology institute, at points bracketing the setpoint, before and after the study. A logger that fails the post-study check has its data invalidated.
3. Confirm measurement uncertainty does not consume more than roughly a quarter to a third of the allowable band; apply uncertainty against the limit for borderline points.
4. Set the logging interval fine enough to capture transients: 1 to 5 minutes for storage units, a few seconds for sterilizer cycles.

5.5 Execute

1. Run storage-unit studies for at least 24 hours, and long enough to capture at least one full defrost cycle; 48 to 72 hours for warehouses to capture day/night cycling.
2. For loaded studies, use the worst-case load and photograph it for reproducibility.
3. For sterilizers, run empty-chamber distribution and loaded heat penetration, and calculate F0 at the cold point alongside a biological-indicator challenge.

5.6 Analyze and set monitoring

1. Identify the hot and cold spots from the logged data.
2. Set the routine monitoring probe at the worst-case position (or a position whose relationship to it is characterized), and set alarm setpoints from the mapped envelope.
3. Where a spot exceeds the band, correct (reduce usable volume, recenter setpoint, fix airflow, or relocate) and re-map to confirm.

5.7 Requalify

Requalify on a risk-based interval and after triggers (section 6.3).

6. Acceptance criteria and requalification

6.1 Study acceptance criteria

• All mapped sensors hold the rated band at steady state.
• Spatial spread at any instant is within the defined limit.
• The control sensor agrees with the co-located logger within the stated tolerance.
• Door-open recovery returns to band within the defined time.
• MKT, where applicable, is at or below the labeled condition.
• All loggers pass post-study calibration; out-of-tolerance loggers invalidate their data.
• Acceptance criteria were defined in the approved protocol before execution.

6.2 Default requalification intervals

6.3 Requalification triggers

Relocation; controller or refrigeration-system replacement or major repair; change in load type or volume; HVAC or room-layout change; new shelving configuration; an excursion investigation implicating distribution.

7. References

21 CFR 211.63, 211.68, 211.142, 211.150 (equipment and warehousing). EU GMP Chapter 3 (premises and equipment); EU GDP Guidelines 2013/C 343/01, section 3.2.1 (initial mapping). ICH Q1A(R2), Stability Testing (for stability-chamber conditions). WHO Technical Report Series guidance on temperature mapping of storage areas. USP General Chapter 1079, Good Storage and Distribution Practices (MKT). ISO 17665 (moist-heat) and ISO 20857 (dry-heat) sterilization, described in original wording; confirm current editions.

Confirm the current version and clause numbers of each reference before issue.

8. Records generated

• Mapping protocol and approved acceptance criteria.
• Sensor placement diagram and location-rationale record.
• Raw logger data files and pre-/post-study calibration certificates.
• Mapping study summary report with identified hot/cold spots and monitoring recommendation.
• Requalification schedule entry.

9. Revision history

10. Approvals

Filled specimen

The following shows the program applied to an example upright pharmacy freezer rated -20 degrees C +/- 5. The specifics are illustrative.

• Studies selected: empty distribution (OQ), loaded distribution (PQ), door-open recovery. Power-loss not required (contents are replaceable).
• Sensor plan: 12 loggers, above the 9 floor: 8 corners, center, one adjacent to the control probe, one just inside the door (warmest expected), one near the coil (coldest expected). Justified by the two suspected extremes.
• Calibration: loggers calibrated at -30 and -15 degrees C, bracketing the setpoint; uncertainty +/- 0.3 degrees C against a +/- 5 band, well inside the one-quarter rule.
• Execution: 48 hour loaded study capturing two defrost cycles; worst-case full load photographed.
• Result: hot spot at the door (T11), cold spot at the coil (T12), both within band outside defrost; routine monitoring probe set at the door zone; alarm setpoints derived from the mapped envelope. All loggers passed post-study calibration.
• Requalification: scheduled at 3 years, with triggers on relocation and refrigeration repair.

In this example the routine probe went to the door, the first-to-excurse position, rather than the geometric center, so live monitoring watches the spot that fails first. That single choice is the point of the whole study.

Common inspection findings this SOP prevents

• Too few sensors, or sensors clustered where it is convenient rather than at the worst case.
• Mapping empty and then storing fully loaded, with no loaded study.
• Acceptance criteria written after seeing the data.
• No post-study calibration, so logger drift is undetectable.
• A routine monitoring probe sitting somewhere other than the qualified worst case.
• Studies too short to capture a defrost cycle; no seasonal re-map of a warehouse.

How to adapt this SOP

1. Set your document number, owner, and effective date, and list your equipment classes in section 2.
2. Point the sterilization cross-reference at your cycle-development procedure.
3. Adjust the default requalification intervals in section 6.2 to your risk assessment.
4. Confirm every standard in section 7 against the current published edition before issue.