January 6, 2020

Amount of water in air

Water by weight contained in 1  m3 of saturated water
( C.A. Cavalli Termodinamica industriale – Hoepli)


Tempearture in oC Contained water (grams of water vapor) g
-10 2.15
0 4.89
10 9.54
20 17.7
30 31.7
40 55.1
50 94.20
60 160.36
70 282.97


Relative humidity is the percentage of water vapor contained in the air contains under certain conditions, that is, in relation to the quantity of water vapor contained in saturated air under same conditions.

For example:

If relative humidity is 80% and the temperature of 20 ° C, since saturated air contains 17.7 g / m3, the air taken from environment is considered to contain 80% of the water, or better 0.8×17.7 = 14.6 grams of water per m3.

Data table (grams of water per mas a function of temperature)

t (oC) -10 0 10 20 30 40 50 60 70
x (g) 2.15 4.89 9.54 17.7 31.7 55.1 94.2 160.36 282.97


Graph (grams of water per m3 as a function of temperature)