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

Water Vapor in Air Reference Data

21 rows

Water vapor content in air (kg per 100 m³) at various dry bulb temperatures and relative humidities
Dry Bulb Temperature(°C)	100% RH(kg/100 m³)	85% RH(kg/100 m³)	80% RH(kg/100 m³)	75% RH(kg/100 m³)	70% RH(kg/100 m³)	65% RH(kg/100 m³)	60% RH(kg/100 m³)	55% RH(kg/100 m³)	50% RH(kg/100 m³)	45% RH(kg/100 m³)	40% RH(kg/100 m³)	35% RH(kg/100 m³)	30% RH(kg/100 m³)
32	3.39	2.89	2.72	2.55	2.38	2.19	2.04	1.93	1.7	1.53	1.36	1.19	1.02
31	3.22	2.73	2.57	2.41	2.25	2.1	1.93	1.77	1.61	1.45	1.29	1.13	0.97
30	3.05	2.59	2.44	2.29	2.13	1.97	1.83	1.67	1.52	1.37	1.22	1.07	0.91
29	2.89	2.45	2.31	2.17	2.02	1.88	1.73	1.59	1.45	1.3	1.16	1.01	0.87
28	2.73	2.32	2.19	2.05	1.91	1.78	1.64	1.5	1.37	1.23	1.1	0.96	0.82
27	2.59	2.2	2.07	1.94	1.81	1.68	1.55	1.42	1.29	1.16	1.03	0.91	0.78
26	2.45	2.08	1.96	1.83	1.71	1.59	1.47	1.34	1.22	1.1	0.97	0.86	0.73
25	2.31	1.97	1.85	1.73	1.62	1.5	1.39	1.27	1.16	1.04	0.93	0.81	0.69
24	2.19	1.86	1.75	1.64	1.53	1.42	1.31	1.2	1.09	0.98	0.87	0.77	0.66
23	2.06	1.76	1.63	1.55	1.45	1.34	1.24	1.14	1.03	0.93	0.83	0.72	0.62
22	1.95	1.66	1.56	1.46	1.36	1.27	1.17	1.07	0.98	0.88	0.78	0.68	0.59
21	1.84	1.56	1.47	1.38	1.29	1.2	1.1	1.02	0.92	0.83	0.74	0.67	0.55
20	1.74	1.48	1.39	1.3	1.22	1.13	1.04	0.98	0.87	0.78	0.69	0.61	0.52
19	1.63	1.39	1.31	1.23	1.15	1.06	0.98	0.9	0.82	0.74	0.65	0.57	0.49
18	1.54	1.31	1.24	1.16	1.08	1	0.93	0.85	0.77	0.69	0.62	0.54	0.46
17	1.45	1.24	1.16	1.09	1.02	0.94	0.87	0.8	0.73	0.65	0.59	0.51	0.44
15	1.29	1.1	1.03	0.97	0.9	0.84	0.77	0.71	0.66	0.58	0.52	0.45	0.39
10	0.94	0.8	0.76	0.71	0.66	0.61	0.57	0.52	0.47	0.43	0.38	0.33	0.28
0	0.49	0.41	0.39	0.37	0.34	0.32	0.29	0.27	0.24	0.22	0.2	0.17	0.15
-5	0.33	0.28	0.26	0.25	0.23	0.21	0.2	0.18	0.16	0.15	0.13	0.11	0.1
-10	0.22	0.18	0.17	0.16	0.15	0.14	0.13	0.12	0.11	0.1	0.09	0.08	0.06

Source: engineeringtoolbox.com

Humidification Calculation

The required amount of steam or water to humidify air can be calculated from the difference in vapor content:

$\Delta w = w_{final} - w_{initial}$

Where:

$\Delta w$ = Amount of water vapor required (kg per 100 m³)
$w_{final}$ = Final vapor content at target temperature and humidity (kg per 100 m³)
$w_{initial}$ = Initial vapor content at starting conditions (kg per 100 m³)

Unit Conversion Note

The table values represent vapor content in $\text{kg per 100 m}^3$ air volume. For calculations using humidity ratio $x$ (mass of water vapor per mass of dry air), convert using:

$x = \frac{w}{\rho_{air}} \quad \text{(kg/kg dry air)}$

Where $\rho_{air}$ is the air density at the actual temperature.

Interactive Charts

Water Vapor in air vs. dry bulb temperature and relative humidity

References

Original Source

Source: engineeringtoolbox.com