Have you ever arrived after a long flight feeling tired, head-achy, and with a sore throat and congested nose?
Have you ever had a slight touch of grogginess, dry eyes, and dry skin?
Humidity is too low in the crew rest compartment and it makes rest less efficient.
Dehydration is a degenerative process and the recovery phase lasts long after a flight. Exposure to dry air also weakens the immune system.