At 20C, the maximum water content in air is 17.3 x 10^-3 kg/m^3.
At 15% relative humidity, then, you can extract a maximum of 0.15 x 17.3g = 2.6g from every 1,000L of air.
If a person needs 5L/day for survival (I am making this up), then you’d need to dry out 5000 / 2.6 = 1,923L of air each day — that’s just short of two cubic meters…
If the density of people living in an area is 50 per square km, drying the air out to extract water would deplete the first meter of the atmosphere by 10%.
At 15% relative humidity, then, you can extract a maximum of 0.15 x 17.3g = 2.6g from every 1,000L of air.
If a person needs 5L/day for survival (I am making this up), then you’d need to dry out 5000 / 2.6 = 1,923L of air each day — that’s just short of two cubic meters…
If the density of people living in an area is 50 per square km, drying the air out to extract water would deplete the first meter of the atmosphere by 10%.