Ask TreeHugger: Airplanes and Personal Air Cleaners

Question: I travel a lot for work. Lately, every time I take a trip on an airplane, I seem to get a headache or get sick. I have seen advertisements for several personal air cleaners or for air purifiers that I can screw onto the fresh air nozzle above my seat and have been thinking of buying one. Do they work?

Response: Airplanes are a unique environment. Many airplanes fly at altitudes greater than 30,000 feet, where the air contains little oxygen and is at temperatures well below freezing. As a result, the air in the plane cabin is pressurized and controlled through environmental control systems, which are designed to regulate cabin pressure, ventilation, temperature, and humidity. As concluded by a National Academy of Science (NAS) panel to investigate air quality inside planes, these environmental control systems, when operated properly, provide enough air to pressurize the cabin, meet general comfort conditions, and minimize smells, heat, and pollution.
Even with these control systems, however, you can still be exposed to pollution that comes from outside or inside the airplane, such as ozone that enters from outside when airplanes are traveling at high altitudes; lubricating oils, deicing fluids, and other industrial pollutants from normal plane operations; organic pollutants (such as pesticides) that come from cleaning products and cabin materials; and smells and allergic and infectious agents that come from passengers. Scientific studies conducted to date have shown that pollutant exposures are generally low and within US and European health limits. Given the small number of studies, however, the NAS panel for air quality inside planes specifically recommended that additional studies on pollutant exposures in planes be performed, including studies to examine the need for installing air-cleaning equipment to remove particles and vapors from the air inside the planes.

Until these studies are performed, personal air cleaners or air purifiers, such as the one that you mentioned, have been suggested as one method to prevent or minimize these exposures. While available personal air cleaners are based on different cleaning technologies, they all work under the general assumption that the person wearing or using the air cleaner breathes only the air that passes through the cleaner. This assumption cannot be true, given the way that air moves in air planes. A mixture of pressurized (and otherwise treated) fresh and recirculated air enters the airplane cabin through overhead outlets or vents. Once inside the cabin, the air can travel throughout the cabin, generally moving in a circular pattern before leaving the plane cabin through floor grilles or overhead intakes. As a result of this circular movement, passengers breathe air that enters the cabin not only from the overhead vent directly above them, but also from other overhead vents throughout the cabin, including those to the side, front, and back of them. Also, since air enters the personal breathing space from all angles, it is simply not possible for one personal air cleaner or purifier to clean the air breathed in by a person(especially since personal air cleaners generally clean air at a rate much lower than the amount of air breathed in by a person).

More detailed information on the recommendations and findings of National Academy of Sciences panel can be found here, while additional information on air cleaners can be found on my previous Ask Treehugger column. Information on environmental concerns over airplane travel can also be found on this Treehugger post.

Previous Ask Treehugger columns can be found here.

Helen Suh MacIntosh is a professor in environmental health at Harvard University and studies how pollution behaves in the environment and how it affects people's health. Please keep in mind that her answers are just her interpretation of available information and should not be taken as the only viewpoint or solution to a problem. Use this column at your own risk. Having said this, please feel free to post any of your environmental health questions to (please use a descriptive email subject line and mention if you want to remain anonymous or not).

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