Guide · Excursions
How to investigate a cold room or freezer temperature excursion.
An excursion is not closed when the temperature recovers. It is closed when you know how long, how far, why, and what happens to the product.
Collect the facts first
| Fact | Why it matters |
|---|---|
| Start and end time | Duration drives the product impact assessment |
| Peak temperature | How far outside the range the unit went |
| Units and product affected | Which batches need a disposition |
| Shift | Who was on duty and who was alerted |
| Alarm history | When people were told and when they acted |
| Door events | Whether the door was open during the event |
Common causes to check
- Compressor or refrigeration failure.
- Door left open or opened too often during loading.
- Hot product loaded in bulk.
- Sensor placement or sensor fault rather than a real excursion.
- Power or communication loss.
Investigation steps
- Quarantine affected product until QA decides.
- Pull the readings, alarms and acknowledgements for the period.
- Compare with the unit’s recent drift and with other units on the same circuit.
- Identify the most likely cause and record the evidence.
- Assess product impact using the stability data your QA team holds.
- Record the disposition and any corrective and preventive action.
How ColdWatch does it
ColdWatch monitors freezers from −80 °C to cold rooms at 2–8 °C, plus product probes and door contacts, on the sensors you already have, over BACnet/IP or Modbus TCP. It raises five alarm types (high, low, rate of change, comms gap and sensor failure) and escalates by screen, email, SMS and push until someone acknowledges with a mandatory comment. AI projects drift forward to say which unit is likely to breach next and roughly when. Excursions go into a register with duration, peak, shift and severity; calibration due dates are tracked with reminders at 30, 15 and 7 days; and every reading, alarm and action is kept in an append-only ALCOA+ audit trail for five years, with IQ/OQ/PQ documents delivered as part of go-live.
Questions
How do you investigate a temperature excursion?
Quarantine the product, collect start and end times, peak, affected units, shift, alarm and door history, identify the likely cause, assess impact with QA’s stability data and record the disposition and CAPA.
What causes cold room excursions?
Commonly compressor failure, doors left open during loading, warm product loaded in bulk, power or communication loss, and sensor faults or poor sensor placement.
Is every out-of-range reading a real excursion?
Not always. A sensor fault or poor placement can look like an excursion, which is why sensor-failure alarms and calibration records matter.
See it on your own data. ColdWatch — Every freezer, every minute. Book a 30-minute working session with an engineer.