Relative Humidity Health

Overview

Engineering reference data for Relative Humidity Health in air psychrometrics.

Key Formulas

Humidity Ratio

$\omega = 0.622 \frac{P_v}{P_a}$

Mass of water vapor per mass of dry air.

Relative Humidity

$\phi = \frac{P_v}{P_{vs}} \times 100\%$

Ratio of actual to saturation vapor pressure.

Wet Bulb Temperature

$T_{wb} = T_{db} - \frac{P_{vs} - P_v}{\gamma}$

Temperature measured by wet-bulb thermometer.

Enthalpy of Moist Air

$h = c_p T + \omega h_g$

Sensible + latent heat per unit mass of dry air.

Variables

Symbol	Description	Unit
$\omega$	Humidity ratio	kg/kg
$\phi$	Relative humidity	%
$P_v$	Vapor pressure	Pa
$P_{vs}$	Saturation vapor pressure	Pa
$T_{db}$	Dry bulb temperature	°C
$T_{wb}$	Wet bulb temperature	°C

Health-Related Relative Humidity Ranges

To maintain healthy indoor air quality, relative humidity (RH) should be managed within specific ranges that inhibit or control various biological and chemical threats. The following table summarizes recommended RH levels for different health factors.

Maintaining humidity within the 40-60% RH range is often cited as a good compromise that addresses many health concerns simultaneously, balancing the need to inhibit biological contaminants (like viruses and mites) with the need to minimize chemical interactions and mold growth.

Interactive Charts

References

• Original Source