Rosacea Treatment Research

Airliner Cabin Relative Humidity

Have you ever experienced discomfort (such as dry eyes) on a long airline flight? It's caused by a low relative humidity level in the cabin, and you can solve it by hydrating yourself before flying.

A relative humidity above 70 percent can cause serious deterioration (such as mold and corrosion) to building materials, but a low relative humidity can cause different kinds of deterioration (shrinking wood, cracking paint) as well as discomfort for humans. The other human factor is disease. Mold and bacteria grow better in more humid environments, but a dry environment can be detrimental to the mucus linings of the respiratory system, which are a first line of defense against disease. People start to complain when relative humidity gets below 25 percent or above 60 percent.₁

However, pressurized aircraft cabins are notorious for their low humidity. In 1999, Boeing admitted that aircraft "typically operate in the 10-15 percent relative humidity range."₂ Cabin air is pressurized, and fresh air comes from bleed air extracted from the engines in older planes (or compressors in newer planes).₃ The relative humidity of outside air decreases drastically at higher altitudes. Unfortunately, studies have shown that attempting to increase the humidity of cabin air by reducing the flow of dry air from outside the plane leads to a different set of health complications due to the increase of contaminants.

To compensate for the dry conditions onboard a commercial airplane, we recommend hydrating yourself by drinking water before boarding the plane. This will help prevent the dry eyes and discomfort caused as your body's water is sucked away by the dry air.

Sources:

1. Relative Humidity by Joseph Lstiburek, Ph.D., P.Eng.
2. Airliner Cabin Air from AirlineSafety.com (Boeing's current cabin air statement)
3. Pressurized cabin from Wikipedia