How to Map a Temperature-Controlled Storage Area
Find where the storage area is actually out of range, then control those places.
What a how-to is not
A how-to is SPEQ’s practitioner method, not a procedure. It does not replace your own SOP, it is not a validated approach, and the judgement calls in it belong to your quality unit.
Temperature mapping establishes the real distribution of temperature across a storage area under the conditions it operates in, so that monitoring sensors can be placed where they will detect a genuine excursion. A store monitored at a single convenient point is monitored at the one place nobody needed to know about, and mapping is what turns a monitoring system from decoration into a control.
- 1
Define the area, its loading pattern and the conditions to be tested
Establish the acceptance range, the physical volume, the racking layout, and how the space is actually loaded. A mapping performed on an empty warehouse describes an empty warehouse, and airflow with product in it behaves differently.
- 2
Place sensors to find extremes, not to confirm the middle
Distribute loggers to cover corners, near doors, close to heating and cooling sources, at high and low racking levels, and in the geometric centre. The purpose is to locate the worst places, so placement is deliberately adversarial rather than representative.
- 3
Run long enough to capture the real cycles
Cover the equipment cycles, the working day with its door openings, and a period of no activity. A mapping run over a quiet weekend measures the easiest conditions the area will ever see.
- 4
Test the seasonal extremes or justify not doing so
Summer and winter behave differently, especially near external walls and roof spaces. Where only one season is mapped, the justification has to be evidence-based rather than a scheduling convenience.
- 5
Challenge the failure modes you will actually face
Power interruption, door left open, refrigeration failure. Knowing how long the area holds range without power is what determines whether a two-hour outage needs a product impact assessment or not.
- 6
Place permanent monitoring at the extremes the mapping found
Sensors go at the hottest and coldest points identified, with alarm limits set to give time to act before the acceptance range is breached. Then re-map after any change to layout, capacity, or the equipment serving the area.
- !Mapping performed empty, so the airflow measured is not the airflow product will sit in.
- !A study run over a quiet period, capturing the easiest conditions rather than the working ones.
- !Permanent sensors placed for convenience rather than at the extremes the mapping identified.
- !No re-mapping after racking, capacity or equipment changed, leaving the study describing a former room.
How to Map a Temperature-Controlled Storage Area: frequently asked questions
Common questions on map a temperature-controlled storage area.
How many loggers does a mapping need?
Enough to characterise the volume and to find its extremes — driven by size, geometry, racking and the number of heat sources rather than by a fixed number. The defensible answer is a rationale that explains the placement; a number without a rationale is arbitrary whether it is high or low.
Does mapping have to be repeated?
On a periodic basis and after any change that could alter the profile: new racking, changed capacity, a replaced or relocated cooling unit, building work, or a different loading pattern. A mapping study describes a configuration, and when the configuration changes the study describes a room that no longer exists.
Where should permanent monitoring sensors go?
At the hottest and coldest points the mapping identified, because those reach the limit first. Alarm limits are set inside the acceptance range with enough margin to act before product is affected — an alarm that fires as the limit is breached tells you about a deviation instead of preventing one.