What We Breathe When We Fly
From toxic fumes to pesticides, an aviation consultant shares the facts about the air up there.
For years, nothing has freaked out health-anxious fliers—or triggered quite so many popular misconceptions—as the air we breathe on board. How much of the worry is justified remains hotly debated; facts tend to be selected carefully to support opposing views.
Fact: A fully loaded jet has one of the smallest volumes of air per person of just about any enclosed public place. It is a simple matter of space and economics. Planes are tight places to start with, the more densely-packed the better from the standpoint of both revenue-seeking airlines and bargain-seeking fliers.
Fact: How much air we get on board matters. Good ventilation seems to reduce the risk of infection. In 1977, an Alaska Airlines Boeing 737 with 54 people aboard was stuck on the ground in Kodiak, Alaska, for close to four hours without an operating ventilation system; within three days, 72 percent of the passengers showed symptoms of influenza, spread by a single sick passenger. With ventilation turned off, onboard carbon dioxide levels are predicted to rise quickly above “comfort levels” established by ASHRAE, the official standard-setting body. So air travelers may actually face their greatest exposure to airborne germs not while flying but, rather, when the plane pulls up to the gate, the chime sounds, and everybody scrambles, huffing and puffing, to get up and grab their carry-ons and wait for the door to open. That’s also when cabin ventilation switches from air filtered by jet engine–powered systems to other sources of air, including the plane’s auxiliary power unit or the airport’s ground-based, diesel-powered turbines that may lack equally sophisticated germ filters.
Air travelers may actually face their greatest exposure to airborne germs not while flying but when the plane pulls up to the gate.
Fact: Cabin air may be “just as good,” in a sense, as the air in modern office buildings—today’s jets exchange their air completely much more frequently than office buildings do. But each individual flier typically gets only about half the amount of “outside” airflow (roughly 7 to 10 cubic feet every minute) as the national standard-setting experts recommend for indoor environments like offices. More important: airplane cabins cram together lots more breathing humans per square foot than do offices. As in a busy elevator, these “other people” contribute their exhalations and gases and coughs and sweat and dead skin—and their viruses and bacteria—to the airborne mix. Everybody shares.
In other words, germ freaks should probably worry more about proximity to sniffling seat mates than about airflow. As an NYU medical expert observed, air purification can’t protect passengers against the common cold. “All the passenger next to you has to do is sneeze, and you’re done,” he told the New York Times in March 2011.
It is better in First Class—but only because there are fewer passengers sharing the up-front real estate and the air that comes with it. (Very roughly speaking, Economy passengers each have about half the personal space of each Business Class passenger, even less compared to each First Class passenger.) Premium passengers don’t get the “good air” first. It doesn’t emanate from the cockpit, waft its way in relative purity through First Class, then plow back through Economy. In reality, cabin air moves downward from the ceiling along the entire length of most jet airliners and ultimately leaves the cabin through floor ducts or grilles beneath the windows.
Fact: Cabin air is not all “fresh”—only about half comes in from outside the plane through the jet engines. Moving through the engine compressors, the air gets very hot, then is cooled down by heat exchangers and fed into the plane’s main air-conditioning “packs.” This outside fresh air mixes with cabin air that’s been recirculated and fed through high-efficiency “particulate arrestor” filters, which are supposed to clean away impurities. Airlines boast these HEPA filters are the same kind used in hospital emergency rooms, and they do remove microscopic particles larger than 0.3 microns—less than one two-hundredth the width of an average human hair. That’s fine enough to catch pet dander and vapors and bacteria like strep and TB as well as viruses suspended in larger droplets, as in a sneeze.
Fact: Airlines really don’t limit “good air” to cut fuel costs. Nor, by all accounts, do they reduce cabin ventilation rates to save money. Early versions of the Boeing 747 did let pilots reduce ventilation for purposes of “economy”—but that was when half-full planes were not uncommon; new Boeing models reportedly don’t have that option, though pilots can turn off air packs for safety reasons, such as a malfunction. Some Airbus planes do have a “Lo” or “Econ” setting that can reduce airflow about 20 percent on relatively empty flights, but it’s reportedly rarely used. Recirculating some of the cabin air does save fuel—jet engines need to pump less outside air to the cabin—but the savings are modest. And while breathing recirculated air certainly sounds bad, it’s not really like inhaling your neighbor’s breath. Research indicates that, with high-performance filtering and the ceiling-to-floor airflow, re-circulated air is no more likely to transmit disease than outside air is. Happily, and for fairly obvious reasons, lavatory air is exhausted directly overboard, not recirculated back into the passenger cabin.
Happily, and for fairly obvious reasons, lavatory air is exhausted directly overboard, not recirculated back into the passenger cabin.
That doesn’t mean it’s Irish Spring in the cabin, though. Not since 1990 has tobacco smoke billowed from the rear of each section of the cabin, permeating much of the atmosphere (smoking was banned on short flights in 1988), but there remain plenty of other contaminants unique to commercial airplanes:
» Toxic fumes can enter the cabin from engine-oil leaks or oil-seal problems, or via hydraulic or de-icing fluids. Boeing paid a flight attendant an undisclosed sum in late 2011 to settle claims regarding toxic fumes in the cabin of a 2007 flight from Memphis to Dallas.
» Ozone, the key component gas in smog, irritates the nose and eyes; as little as one in ten million parts of air, the most FAA regulations allow in cabins at certain altitudes, can cause airway irritation and reduce lung function. Airlines fly where ozone concentrations are high—between troposphere and stratosphere, particularly near the Poles.
» Pesticides can enter cabins via “disinsection” of aircraft. Some foreign health authorities require arriving planes to be sprayed—sometimes with a neurotoxin called permethrin. The goal is to keep stowaway mosquitoes and rodents from importing tropical diseases like malaria, dengue fever, or Lassa fever from remote areas. The EPA is investigating whether the chemicals affect infant and fetal brain development; a 2012 National Research Council review found pesticides in the cabin to be a “moderate concern.”
» Allergens are inescapable as carriers, for a hefty fee, let small pets fly in under-seat containers in the passenger cabin, suspending dander, skin flakes, and tiny saliva particles in the cabin air. A Swiss report in 2010 found common cat allergens on 100 percent of aircraft seats tested, according to MSNBC. DOT has rejected demands, though, for “peanut-free” areas or a ban on peanuts (that would have eliminated Southwest Airlines’ entire meal service).
» Cosmic radiation from massive solar explosions, normally absorbed or shielded by the Earth’s atmosphere, can be 100 times more intense at jet cruising altitudes and near polar latitudes where that protective atmosphere is thinner. Most experts say not to worry, at least not unless you’re a pregnant crewmember who regularly flies long-haul, but FAA has a handy online tool for concerned fliers to predict their likely radiation dose from planned flights.
Not exactly pleasant, but compare today’s cabin air environment to the so-called Golden Age of elegant air travel in the 1930s. Here’s how legendary aviation writer Ernest Gann described it then:
We sweat in the cockpit, though much of the time we fly with the side windows open. The airplanes smell of hot oil and simmering aluminum, disinfectant, feces, leather, and puke . . . the stewardesses, short-tempered and reeking of vomit, come forward as often as they can for what is a breath of comparatively fresh air.
Kind of makes you appreciate today’s somewhat stuffy cabins.
An excerpt from Full Upright and Locked Position: Not-So-Comfortable Truths about Air Travel Today by Mark Gerchick from W. W. Norton & Company.
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Mark Gerchick, an aviation consultant, has advised some of America’s largest airlines and busiest airports over the past fifteen years. A former chief counsel of the Federal Aviation Administration and senior Department of Transportation aviation official, he lives in McLean, Virginia.
(Airplane seats photo by Sarah Baker on Flickr)
