Production hall and warehouse monitoring: from one sensor to a radio system
In a tall hall the temperature at floor level and under the roof are two different numbers — studies record a gradient of 0.8 to 2.6 °C per metre in the lower layer. A single sensor in the middle of the hall therefore does not describe the conditions people work in or goods are stored in.
EnviSensor Team
In short
- EU law sets the duty, national law sets the numbers: Directive 89/654/EEC requires workplace temperature to be adequate for human beings, and member states translate that into specific minimum values.
- Thermal stratification in tall halls is significant: within 2 m of the floor the gradient runs 0.8–2.6 °C per metre, and roughly 0.5 °C per metre above that.
- Snow weight does not follow snow depth: research documents a 0.45 m cover producing a load of 1.4 kN/m² at a bulk weight above 4.5 kN/m³ during a thaw.
- Snow actions on roofs across Europe are governed by EN 1991-1-3 (Eurocode 1), with ground load values set in each country national annex.
- Humidity drives corrosion: ISO 9223 defines time of wetness as the period when relative humidity exceeds 80% at temperatures above 0 °C.
What the rules require on workplace temperature
At European level the obligation is stated in general terms. Directive 89/654/EEC on minimum safety and health requirements for the workplace provides that during working hours the temperature in rooms containing workstations must be adequate for human beings, having regard to the working methods used and the physical demands placed on workers.
The directive deliberately avoids fixed numbers, because a foundry and a packing line are not comparable. Specific minimum values are set by national implementing law and differ between countries — in Poland, for example, the general health and safety regulation requires at least 14 °C in work rooms and at least 18 °C for light physical work and offices. Before designing a monitoring plan it is worth checking the values in force in the country where the facility operates.
Humidity is rarely regulated by a fixed range for industrial halls. What matters in practice is its effect on the process: condensation on cold surfaces, corrosion of steel components, electrostatic charging in dry conditions, and mould growth at the damp end of the scale.
Why one sensor does not describe a hall
In tall buildings warm air collects under the roof, creating pronounced stratification. A study published in Energies, based on measurements in warehouse buildings, found a vertical temperature gradient of 0.8–2.6 °C per metre within 2 metres of the floor, and roughly 0.5 °C per metre above.
The consequences are practical. A sensor mounted high on a column reports a value that neither the worker nor the goods on the lowest rack level experience. Conversely, a sensor near the floor will not detect overheating in the space under the roof.
How many sensors, and where
- Work zones — at roughly 1.5 m, the height at which workplace requirements are assessed.
- Storage zones — at least the lowest and highest rack levels, since the difference often runs to several degrees.
- Under-roof space — where heat-generating processes run or services are routed below the roof.
- Areas near loading doors — conditions change most abruptly there, and that is where condensation most often occurs.
Humidity, condensation and corrosion
In industrial facilities humidity usually matters more than in offices, because it governs corrosion and product quality. ISO 9223, which classifies atmospheric corrosivity, uses the concept of time of wetness — defined as the period during which relative humidity exceeds 80% at temperatures above 0 °C.
That does not mean corrosion stops below the threshold. The literature indicates an electrolyte film forms at critical humidity in the range of 60–80%, and lower still in the presence of hygroscopic contaminants such as salts — which is why coastal and de-icing environments behave differently from inland ones.
Condensation appears when a surface is colder than the dew point of the air. In winter the most exposed elements are therefore those near doors and external walls rather than the centre of the hall. Humidity monitoring is only meaningful alongside temperature measurement, because only both values together yield the dew point.
Roof monitoring: why snow depth tells you nothing
Snow loading is where intuition misleads most often. What counts is the mass of the cover, not its depth — and mass rises during thaws and when rain falls on snow.
A Building Research Institute monograph reports an average bulk weight of about 2.0–2.5 kN/m³ for cover lying more than two months, but a measurement of over 4.5 kN/m³ during a March 1970 thaw. In that same episode a cover just 0.45 metres deep produced a load of 1.4 kN/m².
Design values for comparison come from EN 1991-1-3 (Eurocode 1), which governs snow actions on structures across Europe. Characteristic ground snow loads are set in each country national annex and vary by zone and altitude, which is why the same roof design carries a different margin in Spain, Poland or Finland. A relatively thin but saturated cover can approach those values.
Who is responsible
In most European jurisdictions the duty to keep a building safe in use rests with its owner or manager, and national building authorities issue winter advisories against allowing structures to become overloaded by accumulated snow. No standard mandates roof-mounted sensors. Monitoring conditions under the roof and on it is, however, a practical way of discharging that duty: it links the temperature record to thaw risk and lets snow clearance be scheduled before the load becomes critical.
Wired or wireless across a large facility
In a hall of several thousand square metres, cabling usually costs more than the sensors. The choice comes down to a simple calculation.
| Situation | Solution |
|---|---|
| A few points near existing network | LAN or PoE logger with wired probes |
| Dispersed points, no power available | 868 MHz LoRa radio sensors with a gateway |
| High-bay racking, metal obstacles | Wireless, but with a range test before final mounting |
| Zones whose layout changes often | Wireless — a sensor moves without re-running cable |
In facilities with many conductive obstacles — metal racking, cold room enclosures — it is worth taking check measurements at the planned sensor locations before finalising gateway placement. That is the only reliable way to assess range in a specific building.
Frequently asked questions
What temperature is required in a production hall?
EU Directive 89/654/EEC requires workplace temperature to be adequate for human beings, having regard to working methods and physical demands, but sets no fixed figure. Specific minimum values come from national implementing law and differ between countries, so the applicable number should be checked for the country where the facility operates.
How many temperature sensors does a hall need?
It depends on height and functional layout rather than floor area alone. Because of thermal stratification — 0.8 to 2.6 °C per metre in the lower layer — it is worth measuring work zones, storage levels and areas near loading doors separately, since conditions there change most abruptly.
Why monitor conditions on a hall roof in winter?
Snow load depends on the mass of the cover, not its depth. Research documents a 0.45 m cover producing 1.4 kN/m² at a bulk weight above 4.5 kN/m³ during a thaw. Tracking the temperature record helps identify the moment snow begins absorbing water and approaching design values set under EN 1991-1-3.
What standard governs snow load on roofs in Europe?
EN 1991-1-3, part of Eurocode 1, covers snow actions on structures. Characteristic ground snow load values are defined in each country national annex and vary by zone and altitude.
Is wired or wireless monitoring better in a hall?
Wired suits a small number of points near existing network infrastructure and delivers power over the same cable. Wireless in the 868 MHz band has the advantage across large sites, where no power is available at the measurement point, and where zone layouts change.
Sources
- Council Directive 89/654/EEC concerning the minimum safety and health requirements for the workplace
- EN 1991-1-3, Eurocode 1: Actions on structures — Part 1-3: General actions, snow loads (CEN)
- J.A. Żurański, A. Sobolewski, Snow load in Poland, Building Research Institute (ITB) monograph, 2009
- Porras-Amores, Mazarrón, Cañas, Study of the Vertical Distribution of Air Temperature in Warehouses, Energies 2014, 7(3)
- ISO 9223 — Corrosion of metals and alloys, corrosivity of atmospheres, classification
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