Warehouse temperature mapping
Large ambient warehouses are dominated by height, external walls, roof and season — so the sensor plan and the study calendar matter more than anything else.
In a 15–25 °C warehouse the challenge is scale. Heat stratifies vertically, external walls and roof track the weather, loading bays admit outside air and forklifts stir it. A useful study samples all of this deliberately.
Sensor plan
- A grid across the floor plan with sensors at low, mid and high rack levels.
- Extra sensors near loading doors, external walls, roof lights, heaters and air-handling units.
- Reference sensors at the existing monitoring points so the two datasets can be compared.
Season and duration
One week in spring does not characterise August. Guidance for large ambient stores is to map in both hot and cold seasons, or to justify why a single season bounds the risk. Keep a record of ambient weather during the study; it is the explanation for most of what the data show.
Stratification is the dominant effect
In a high-bay ambient store the single largest gradient is vertical, and it is often larger than everything else combined. Warm air rises, the roof gains heat from the sun, and the space between the top of the racking and the roof deck becomes a reservoir that feeds back down. Differences of 4 to 8 °C between floor level and the top pick face are routine in an uncontrolled warehouse on a summer afternoon, and it is entirely possible for the floor to sit comfortably at 21 °C while the top pallet is at 27 °C.
This is why a sensor plan that covers the floor plan but not the height characterises a building that does not exist. Sample at least three levels — low pick face, mid racking, top pick face — at every grid position, and put sensors above the top pick face where the stratified air actually sits, even though no product is stored there, because that is where the load on the space comes from.
| Position | What it captures |
|---|---|
| Top pick face, centre of the building | The stratification maximum; usually the hot spot |
| Immediately inside each loading door | Outside air ingress during dispatch; the fastest-moving position |
| Against the south or west external wall | Solar gain through the fabric, hours after the peak outside |
| Under roof lights | Local radiant gain that the rest of the roof does not show |
| Adjacent to heaters and AHU discharges | The equipment's own contribution, which can be an excursion in itself |
| Existing monitoring probe positions | Whether the permanent system represents the worst case |
| Outside, shaded | Ambient reference; the explanation for most of the above |
Duration and season
A week is the usual minimum, and it should be a working week rather than a quiet one: goods in, goods out, doors opening, forklifts running. A study over a closed holiday period characterises a building nobody is using.
Season matters more here than in any other kind of space. One week in spring says nothing about August, and the guidance for large ambient stores is either to map in both hot and cold seasons with an identical sensor plan, or to run the study at the worst season and document why the other is bounded. Record the external air temperature throughout: it is the context that makes the seasonal argument possible and the explanation for most of the features in the data.
Running it in phases
- Large buildings often need more loggers than a site owns. Phasing is legitimate — map one zone, then the next — provided a set of common reference positions is instrumented in every phase.
- Those common positions are what let the phases be stitched together. Without them the datasets share no anchor and cannot be compared.
- Keep ambient conditions comparable across phases, or record the difference and account for it. Two phases a month apart in changing weather are two different buildings.
- State the phasing plainly in the report. It is a limitation, not a flaw, and hiding it makes it one.
Frequently asked questions
- Do ambient 15–25 °C warehouses need temperature mapping?
- Yes. GDP requires mapping of storage areas before use, and ambient stores commonly show the largest gradients — especially at high rack levels in summer.
- How many sensors for a warehouse mapping study?
- Dozens for a typical distribution warehouse; the number follows from the grid spacing, rack heights and risk points, and each location must be justified in the protocol.
References
- [1]WHO Technical Supplement 8 to TRS 961 Annex 9: Temperature mapping of storage areas (2015)
- [2]EU Guidelines on Good Distribution Practice of medicinal products for human use (2013/C 343/01)
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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