For air travellers
All too often, travelling by plane can leave you feeling exhausted and dried out by the time you arrive to your destination. That is a result of an onboard dehydration. The air inside the cabin of a plane usually has a humidity level of 10 to 20 percent which is lower than that of the driest desert on Earth.
Why did you get a splitting headache that lasted the whole flight?
Why did your skin go from "perfect" to dry and wrinkled within a few hours?
Why did you feel so exhausted?
THE ANSWER: Because the air drawn into the plane to pressurize it comes from extremely dry, high-altitude regions of the atmosphere.