Humidity, Airflow and Psychrometric Measurement

Relative humidity expresses current vapour pressure relative to saturation at the same temperature. A temperature change can alter RH even when the amount of water vapour is unchanged.

Dew point describes the temperature at which condensation begins; wet-bulb methods infer moisture state from evaporative cooling. Both require correct technique and interpretation.

Doorways, coils, humidifier outlets, walls and product surfaces can differ sharply. One convenient sensor cannot reveal chamber gradients or the microclimate within a dense load.

Anemometers have minimum reliable velocities and directional limitations. Very low chamber movement may be better assessed through mapping and product response than a single unstable number.

Salt solutions, reference instruments and laboratory calibration may support humidity verification when used within their limitations. Records should identify temperature, stabilisation time and acceptance criteria.

Report temperature with RH, identify location and instrument, and distinguish indicative monitoring from calibrated measurement. Map the loaded chamber after major equipment or airflow changes.