Humidity monitoring in storage areas: when and how
Monitor relative humidity where products or packaging are humidity-sensitive or where labels require it. Sensors drift; calibrate them and expect larger uncertainty than for temperature.
Relative humidity matters for hygroscopic products, moisture-sensitive packaging, and in stability chambers where it is a controlled condition. Warehouses storing ambient products commonly monitor RH to demonstrate it stays below a defined ceiling, though the requirement is often less explicit than for temperature.
Practicalities
- Place RH sensors with temperature sensors: RH is temperature-dependent and a 1 °C error at 50 % RH corresponds to roughly 3 % RH.
- Avoid positions near doors, wet processes and direct airflow from HVAC outlets unless that is where the risk lies.
- Calibrate at points spanning the working range (e.g. 30, 50, 75 % RH) using salt solutions or a humidity generator.
- Set alarm limits with the sensor's uncertainty in mind; a ±3 % RH sensor cannot police a 60 % RH limit at 59 %.
Frequently asked questions
- Do refrigerators need humidity monitoring?
- Rarely. Humidity in a refrigerator is close to saturation and few refrigerated products specify RH; the requirement is product-driven.
References
- [1]WHO Technical Supplement 16 to TRS 961 Annex 9: Environmental temperature monitoring systems for fixed storage areas
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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