Moisture damage in storage areas rarely occurs evenly throughout the entire warehouse. It often first appears in specific locations: on cold exterior walls, in poorly ventilated corners, near the floor, behind shelves, close to doors or in areas with large temperature fluctuations. These are exactly the places where cardboard packaging can soften, metal parts can corrode, packaging can be damaged or sensitive products can lose quality.
The problem: A centrally mounted humidity sensor often shows uncritical values, even though increased humidity or even a risk of condensation already exists in other areas of the warehouse. Anyone who wants to monitor humidity in storage areas reliably should therefore not simply install any sensor, but choose the measuring points correctly. This article explains where humidity sensors should really measure, why several measuring points are often useful and which typical mistakes should be avoided when placing sensors.
Suitable solutions can be found, among others, in the areas of humidity sensors, humidity data loggers and humidity-temperature sensors such as the IFG80 / ITFG80 humidity-temperature sensor.
Table of contents
- Why humidity in storage areas is critical
- Why one central humidity sensor is often not enough
- Relative humidity, temperature and dew point: What really matters
- Exterior walls and cold surfaces: A common cause of local humidity pockets
- Doors, loading ramps and loading areas: Moisture ingress through air exchange
- Shelves, pallets and blocked air circulation
- Floor level and ceiling area: Why measuring height matters
- Several measuring points instead of false security
- Data logger or permanently installed humidity sensor?
- Limit values, alarms and trend monitoring
- Typical mistakes when placing sensors
- Suitable products for humidity monitoring in storage areas
- Practical example: Corrosion despite an uncritical central value
- Conclusion: Humidity must be measured where damage can occur
- FAQ: Frequently asked questions about humidity in storage areas
Why humidity in storage areas is critical
Humidity directly affects many stored goods, packaging materials and components. Metal parts can corrode, cardboard can absorb moisture, paper can warp, electronics can react sensitively and hygroscopic materials can change their properties. Depending on the product, even prolonged elevated humidity levels can be enough to impair quality, function or packaging stability.
Moisture is particularly critical when it does not occur only briefly, but remains present for hours or days. A short humidity increase when a door is opened is not automatically a damage event. However, if humidity remains in a corner, on an exterior wall or behind a shelf, a local microclimate can develop there. These are exactly the areas that are often not detected by a single central sensor.
For many storage areas, the average humidity value is therefore not the only relevant factor. The decisive question is whether there are critical sub-areas. A warehouse may show 50 % relative humidity in the central aisle, while significantly higher values occur behind stored pallets on a cold exterior wall. The goods in this area are then at risk, even though the central sensor appears to give the all-clear.
Reliable humidity monitoring therefore begins with understanding the storage structure. Room size, wall construction, insulation, air exchange, door openings, heating or cooling zones, shelf layout, type of goods and packaging all influence where moisture problems can occur. Sensor placement must take these factors into account.
Why one central humidity sensor is often not enough
In many warehouses, a single humidity sensor is mounted centrally in the room. At first glance, this seems logical because a central sensor provides a general room value. For a rough assessment, this may be sufficient. For preventing moisture damage, however, it is often not enough.
The central area of a warehouse is often better ventilated than peripheral areas. There is more air movement, temperature and humidity are more uniform, and the sensor is usually mounted freely in the room. Critical humidity areas, however, often develop where air is stagnant or where surfaces are colder than the room air. These zones are often not located near the central sensor.
A single sensor can therefore quickly create a false sense of security. It shows the value at its own position, not the worst value in the warehouse. If the measuring point is well selected, this can be helpful. If it is too representative of the uncritical average area, it overlooks local risks.
This is particularly problematic with high-value or sensitive goods. If metal parts, spare parts, electronics, measuring instruments, paper goods, packaging or chemical products are stored, humidity monitoring should not only record the average value. It should also cover the areas where moisture is most likely to cause damage.
Relative humidity, temperature and dew point: What really matters
Many humidity sensors measure relative humidity. This value describes how saturated the air is in relation to the maximum possible amount of water vapor at the current temperature. Relative humidity is therefore always temperature-dependent. Warm air can absorb more moisture than cold air. If the same air cools down, relative humidity increases.
This relationship is especially important for storage areas. A warehouse may have an uncritical relative humidity value in the middle of the room. However, if the air cools down near a cold exterior wall or close to the floor, the relative humidity there can be significantly higher. In extreme cases, condensation occurs. Then it is not only humid air that is being measured; moisture actually settles on surfaces.
Humidity and temperature should therefore always be considered together. A humidity value without temperature is difficult to evaluate. Two areas with the same relative humidity can have different risks if the surface temperatures differ significantly. Conversely, an apparently moderate humidity value can become critical if components, walls or stored goods are significantly colder than the room air.
For many applications, the dew point is also helpful. It indicates the temperature at which the air would be saturated and moisture could condense. If cold surfaces in the warehouse are close to the dew point, the risk of condensation increases, and with it the risk of corrosion or packaging damage.
| Measured value | Meaning | Relevance in storage areas |
|---|---|---|
| Relative humidity | Moisture content relative to the maximum possible moisture at the current temperature | Shows whether the air is dry, normal or critically humid |
| Temperature | Air temperature at the measuring point | Influences relative humidity and condensation risk |
| Dew point | Temperature at which condensation can begin | Helps assess cold walls, goods and surfaces |
| Measurement duration | Humidity trend over time | Shows whether humidity is only briefly or permanently critical |
In practice, this means: A good measuring point does not simply record a convenient average value, but shows the real risk to the stored goods. This includes temperature, humidity, time profile and proximity to critical surfaces.
Exterior walls and cold surfaces: A common cause of local humidity pockets
Exterior walls are particularly common problem areas in warehouses. They can be colder than the room air, especially with poor insulation, large temperature differences between inside and outside or uneven heating. When warm, humid air meets a cold wall, the relative humidity rises locally. Under unfavorable conditions, condensation can form.
A sensor in the middle of the room often does not detect this risk. There, the air is warmer and better mixed. Directly on the exterior wall or behind a shelf, the situation can be completely different. North-facing walls, poorly insulated wall sections, base zones, corners, areas behind pallets and wall sections with little air circulation are especially critical.
Humidity sensors should therefore not simply be mounted directly on the wall without thought. A sensor sitting directly on a cold wall may record a very local wall value that does not necessarily represent the air conditions around the goods. A measuring point near the critical zone is often useful, but it should be positioned so that the air in the goods area is measured. If condensation is suspected, additional surface temperature measurement may be useful.
If damage repeatedly occurs on the same wall side, targeted measurement should be carried out there. A data logger can show over several days or weeks whether humidity increases at night, during weather changes, after door openings or under certain operating conditions. This makes it possible to distinguish between a permanent problem and recurring peaks.
Doors, loading ramps and loading areas: Moisture ingress through air exchange
Doors, loading ramps and goods receiving areas are typical entry points for moisture. When a door is opened, outside air flows into the warehouse. Depending on the season, this air can be warm and humid or cold and dry. Transitional seasons, rainy days, fog, high outdoor humidity and frequent door openings are particularly critical.
Strong fluctuations often occur near doors. A sensor directly next to the door can show very dynamic values that do not necessarily describe the condition of the entire warehouse. At the same time, goods near the door can be more heavily exposed than goods in the middle of the room. It should therefore be decided whether a sensor is intended to capture a general storage value or specifically monitor the exposure in the loading area.
For humidity monitoring, it can be useful to record door areas separately. This makes it visible whether humidity events are related to goods receipt, truck unloading or frequent opening. If humidity values drop quickly again after the door is closed, the risk may be lower. If they remain elevated for a long time, poor air circulation or insufficient dehumidification may be present.
Storage organization also plays a role. Sensitive goods should ideally not be stored permanently directly in door areas or near cold ramp zones. A sensor can help support this assessment with measurement data.
Shelves, pallets and blocked air circulation
Shelves and pallets change the air circulation in storage areas. Between closely spaced shelves, behind high stacks of goods or directly against walls, areas can develop where air hardly moves. Moisture can remain there longer than in open areas.
This is particularly relevant when goods are stored directly along exterior walls. Even a small gap between goods and wall can create a poorly ventilated space. The air there cools down, humidity rises locally, and the goods are more heavily exposed than the central sensor would suggest.
Sensors should therefore not only be mounted where they are easy to access. They should also take into account the areas where air circulation is restricted. In some warehouses, a measuring point behind or between shelves is much more meaningful than a sensor in the main aisle.
At the same time, the sensor should not be mounted so hidden that it only measures an extremely local special condition. The goal is a measuring point that realistically represents the critical goods area. In complex storage layouts, it is often better to use several measuring points: one central reference point and additional sensors in known risk zones.
Floor level and ceiling area: Why measuring height matters
Humidity can differ depending on the height within the warehouse. Near the floor, surfaces are often cooler, especially with unheated floors, ramps, poorly insulated floor slabs or areas with little air movement. Humidity can behave differently there than at head height or in the upper hall area.
The ceiling area can also be relevant. Warm air rises, and depending on hall construction, roof insulation and ventilation, different temperature and humidity conditions can occur there. In high halls, layers can form. A sensor at a height of two meters does not automatically describe the conditions in the upper rack area or below the roof.
The correct measuring height depends on the goods. If sensitive products are stored on pallets near the floor, at least one measuring point should record the conditions in this area. If goods are stored in high racks, additional measuring points at different heights can be useful. Especially in high halls, measuring only at eye level is often not sufficient.
Heating systems, ventilation outlets and air curtains can also influence vertical distribution. A sensor directly in the airflow then shows the effect of the system rather than the real storage condition at the goods. Measuring points should therefore be selected so that they are not distorted by direct airflows or local heat sources.
Several measuring points instead of false security
In many warehouses, a single measuring point is not enough. This is especially true for large halls, different storage zones, exterior wall areas, doors, high racks, separate temperature zones or moisture-sensitive goods. Several measuring points make it visible whether the warehouse is truly homogeneous or whether individual areas differ significantly.
A sensible concept often consists of one central reference sensor and several additional measuring points in risk areas. The central sensor shows the general storage condition. The additional sensors show whether local humidity pockets exist. This prevents the average value from hiding a critical local problem.
The number of measuring points depends on warehouse size, value of goods, risk profile and desired documentation. For simple storage areas, one additional data logger on a critical exterior wall can already provide important insights. For larger or quality-critical warehouses, several permanently installed humidity sensors with data transmission may be useful.
| Measuring point | Why useful | Typical benefit |
|---|---|---|
| Central storage area | Reference for general room condition | Comparison value for other measuring points |
| Exterior wall | Detects local humidity caused by cold surfaces | Early indication of condensation risk |
| Door or loading area | Records moisture ingress through air exchange | Assessment of goods receipt and door openings |
| Between shelves | Detects poor air circulation | Protects sensitive goods in densely stored areas |
| Floor level | Records cool and poorly ventilated zones | Important for pallet storage and metal parts |
| Upper rack area | Records vertical differences in high halls | Assessment of high-rack storage and roof proximity |
Several measuring points are not only helpful for monitoring, but also for root cause analysis. If only one sensor is available, it remains unclear whether a problem is local or general. With several measuring points, it becomes possible to identify whether moisture exposure comes from outside, poor air distribution or specific operating processes.
Data logger or permanently installed humidity sensor?
There are basically two common approaches to humidity monitoring in storage areas: permanently installed sensors and mobile or temporary data loggers. Both have their place. The right choice depends on whether continuous monitoring is required or whether the first step is analysis.
A permanently installed humidity sensor is useful when a storage zone is to be continuously monitored and, if necessary, connected to a building management system, PLC, display or alarm. Such sensors are particularly suitable for permanent measuring points where the location is already known and needs regular monitoring.
A data logger is especially helpful when the cause of a problem is being investigated or when it is first necessary to find out where critical humidity values occur. It can be used at different locations over days or weeks and shows the time profile. This makes it visible whether humidity values rise at night, occur after door openings, are related to weather changes or appear only in certain storage zones.
In practice, a combination is often useful. First, data loggers are used to identify critical zones. Then, permanent sensors are installed at the most important points. This avoids installing permanent measuring points in uncritical or insufficiently meaningful locations.
Limit values, alarms and trend monitoring
A humidity sensor is only truly useful if the measured values are evaluated correctly. A single limit value can be helpful, but it is not always sufficient. It is also important how long a value is exceeded and how humidity and temperature develop over time.
For sensitive stored goods, a short-term humidity increase may be less problematic than moderate but permanently elevated humidity. An alarm based on a fixed limit value should therefore match the goods, packaging and storage process. If the limit value is set too low, unnecessary alarms occur. If it is set too high, critical developments are detected too late.
Trend monitoring is particularly helpful. Does humidity rise every evening? Does it remain elevated for a long time after door openings? Are there differences between summer and winter? Does a measuring point change after shelves are rearranged or ventilation is adjusted? Such questions can only be answered if measured values are stored and not only read momentarily.
For quality-relevant storage areas, documented humidity monitoring can also be important internally. It shows that storage conditions are being controlled and supports evaluation in the event of complaints, corrosion cases or packaging damage.
Typical mistakes when placing sensors
A common mistake is mounting the sensor in a convenient but not meaningful location. The sensor is then easily accessible in the central aisle, but does not measure where goods are at risk. The result is a stable measured value that does not represent the actual risk areas.
Another mistake is mounting the sensor directly next to doors, heaters, ventilation outlets or windows without clarifying the measuring task. Such locations can be useful if exactly this area is to be monitored. However, they are unsuitable if a general warehouse value is required. The sensor then measures local influences instead of representative storage conditions.
Mounting directly on cold exterior walls can also be problematic. If the sensor is too close to the wall, it may measure an extreme local zone. This can be useful for damage analysis, but not necessarily for assessing the air conditions around the goods. Here it must be clearly decided whether the wall risk, goods zone or general room condition is to be measured.
Finally, sensors are often used too late. Measurements are only taken once damage is already visible. It is better to record humidity trends early, especially after modifications, changes to storage areas, ventilation adjustments or the storage of moisture-sensitive products.
| Mistake | Why problematic | Better approach |
|---|---|---|
| Only one central sensor | Local humidity pockets remain undetected | Use additional measuring points in risk zones |
| Sensor directly in airflow | Measured value shows ventilation influence instead of storage condition | Place sensor outside direct air outlets |
| Sensor directly on cold wall | Measured value may be too local or not representative | Clarify measuring target: wall risk or goods area? |
| No long-term recording | Humidity peaks and recurring patterns remain hidden | Use data loggers or continuous measured value storage |
| No temperature measurement | Humidity value cannot be properly evaluated | Measure humidity and temperature together |
Suitable products for humidity monitoring in storage areas
For fixed measuring points in warehouses, humidity sensors are suitable. They record relative humidity and temperature and, depending on the version, can be connected to a display, control system or building management system. Such sensors are useful when defined storage zones are to be monitored permanently.
The IFG80 / ITFG80 humidity-temperature sensor is suitable for measuring relative humidity and temperature and can be used in rooms or air ducts. For storage applications, it is particularly interesting when a fixed humidity and temperature measurement is required in a hall or defined storage area.
For temporary measurements, root cause analysis and long-term recording, humidity data loggers are useful. They can be placed at different points in the warehouse to identify critical zones. Data loggers such as the testo 175 H1 temperature and humidity data logger are suitable for documenting temperature and relative humidity in buildings and closed rooms.
If several measuring points or external sensors are required, a climate data logger such as the testo 176 H2 climate data logger for humidity and temperature may also be of interest. The selection depends on whether short-term analysis, permanent monitoring, local alarming or long-term documentation is required.
Practical example: Corrosion despite an uncritical central value
In a warehouse, metal parts are stored in cardboard boxes and plastic containers. The central humidity sensor shows values over several weeks that are considered uncritical. Nevertheless, slight corrosion marks appear on certain metal parts. What stands out is that the affected parts almost always come from the same storage area.
At first, it is assumed that the parts were already delivered damp or that the packaging is unsuitable. On closer inspection, however, it becomes apparent that the affected area is located on an exterior wall. Pallets are stored very close to the wall there, and there is hardly any air movement between wall and goods. The central measuring point in the main aisle does not record this area.
For root cause analysis, several humidity data loggers are used: one in the central aisle, one directly in the affected shelf area, one near the wall behind the pallets and one close to the floor. After a few days, a clear picture emerges. While the central sensor records uncritical values, humidity and temperature differences near the wall regularly increase. Especially at night and after humid outdoor days, humidity remains elevated there for a long time.
The cause is therefore not a general storage problem, but a local humidity pocket. The measures are adjusted accordingly: The pallets are stored with a distance from the exterior wall, air circulation is improved, particularly sensitive goods are moved to a less critical area and an additional humidity sensor permanently monitors the critical zone.
The example shows why a single measured value is not enough. Moisture damage occurs where the goods are stored, not where the sensor was conveniently mounted.
Conclusion: Humidity must be measured where damage can occur
Moisture damage in storage areas can only be reliably avoided if the measuring points are selected sensibly. A central humidity sensor can provide a good overview, but it does not automatically detect local humidity pockets on exterior walls, near doors, behind shelves, near the floor or in poorly ventilated zones.
For a reliable assessment, humidity and temperature should be measured together. Measuring points in areas where sensitive goods are stored or where moisture is known to occur are particularly important. Several measuring points and long-term recordings help make critical patterns visible and derive targeted measures.
Suitable solutions can be found in the areas of humidity sensors, humidity data loggers and humidity-temperature sensors such as the IFG80 / ITFG80. The decisive factor is not only the measuring device, but the correct placement in the warehouse.
FAQ: Frequently asked questions about humidity in storage areas
Where should humidity be measured in a warehouse?
Humidity should be measured where the goods are actually at risk. In addition to a central reference point, measuring points on exterior walls, near the floor, in shelf areas, near doors and in poorly ventilated zones are useful.
Is one central humidity sensor in the warehouse sufficient?
For rough room monitoring, a central sensor may be sufficient. However, for preventing moisture damage, it is often not enough because local humidity pockets on walls, behind shelves or near the floor can remain undetected.
Why do metal parts corrode despite normal humidity in the warehouse?
The cause may be a local humidity problem. The central sensor may show uncritical values, while significantly higher humidity occurs on a cold exterior wall or in a poorly ventilated shelf area.
What role does temperature play in humidity measurement?
Relative humidity is temperature-dependent. If air cools down on cold surfaces, relative humidity rises locally. Humidity and temperature should therefore always be considered together.
Should a humidity sensor be mounted directly on the exterior wall?
Not automatically. An exterior wall can be an important risk area, but a sensor directly on the wall may measure too locally. A better position is one that realistically represents the critical goods area near the wall.
Why are several measuring points useful in storage areas?
Several measuring points show differences between the central storage area, exterior wall, door area, shelf zone and floor level. This makes local humidity pockets visible that a single sensor would miss.
When is a humidity data logger useful?
A humidity data logger is useful when humidity trends over several days or weeks need to be investigated. It helps identify recurring patterns, humidity peaks and critical storage areas.
Which is better: permanently installed sensor or data logger?
A permanently installed sensor is useful for continuous monitoring. For root cause analysis, temporary measurements or searching for critical areas, a data logger is often better. In many cases, a combination of both solutions is ideal.
What are typical mistakes in sensor placement?
Typical mistakes include using only one central sensor, mounting directly in airflow, mounting at a non-representative point, missing temperature measurement and missing long-term recording.
Which products are suitable for humidity monitoring in storage areas?
Suitable products include humidity sensors for fixed measuring points, humidity data loggers for long-term recording and humidity-temperature sensors such as the IFG80 / ITFG80.