Refrigerator temperature mapping
Pharmacy and laboratory refrigerators are small, but they have cold spots at the back and warm spots in the door — mapping shows which shelves are safe.
A domestic-style refrigerator can freeze product at the back wall and let it warm in the door. Purpose-built pharmacy units are better, but every unit should be mapped before it stores product.
A practical plan
- Five to nine sensors: each shelf level, back and front, plus the door compartment if it is used and the centre.
- Sampling every one to five minutes; door-opening events are short.
- At least 24 hours, ideally longer, under the loading condition that will be used.
- Include an open-door test if the protocol calls for one, and record how long recovery takes.
Outcome
The result is a shelf-by-shelf statement of which positions stay within 2–8 °C, which are excluded, and where the monitoring probe should live — usually in a buffered form representing product, at or near the warmest acceptable position.
Frequently asked questions
- Can a domestic refrigerator be used for medicines?
- Only if mapping shows the positions used stay within 2–8 °C without freezing, and monitoring with alarms is in place. Many domestic units freeze product at the back wall and warm it in the door.
- Where should the monitoring probe be placed in a pharmacy refrigerator?
- At or near the warmest acceptable product position identified by mapping, usually buffered (e.g. in a glycol vial) to represent product rather than air.
References
- [1]WHO Technical Supplement 8 to TRS 961 Annex 9: Temperature mapping of storage areas (2015)
General technical guidance written against the cited sources. It is not regulatory or legal advice and does not replace the applicable standard, guideline or a qualified reviewer's judgement.
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