1. What is Relative Humidity (RH)?

Definition: Relative humidity is the ratio of the current amount of water vapor in the air to the maximum possible amount at that temperature, expressed as a percentage.

Purpose: RH is crucial for weather forecasting, HVAC systems, industrial processes, and maintaining comfortable indoor environments.

2. How Does the RH Calculator Work?

The calculator uses the formula:

Where:

• \( RH \) — Relative Humidity (%)
• \( e \) — Actual vapor pressure (Pa)
• \( e_s \) — Saturation vapor pressure at the same temperature (Pa)

Explanation: The actual vapor pressure is divided by the saturation vapor pressure and multiplied by 100 to get a percentage.

3. Importance of Relative Humidity

Details: Proper RH levels affect human comfort, prevent mold growth, preserve materials, and are critical in many industrial and agricultural processes.

4. Using the Calculator

Tips: Enter both vapor pressures in Pascals (Pa). The saturation pressure must be ≥ actual vapor pressure. Typical values range from 600 Pa to 3000 Pa depending on temperature.

5. Frequently Asked Questions (FAQ)

Q1: How do I find vapor pressure values?
A: Use psychrometric charts, equations like Magnus formula, or measure with hygrometers and convert to vapor pressure.

Q2: What's a comfortable RH range for humans?
A: Typically 30-60%. Below 30% can cause dryness, above 60% promotes mold growth.

Q3: Does temperature affect RH?
A: Yes, since saturation vapor pressure (eₛ) changes with temperature while actual vapor pressure (e) may remain constant.

Q4: What's the relationship between dew point and RH?
A: Dew point is the temperature at which RH would be 100%. Higher dew points indicate more moisture in the air.

Q5: Why does RH change throughout the day?
A: RH varies inversely with temperature when moisture content is constant - higher in cool mornings, lower in warm afternoons.