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 SEATTLE, July 29 /PRNewswire/ -- Boeing took steps this week to reassure its customers and their passengers about the safety and effectiveness of the air distribution systems in Boeing airliners, Boeing Commercial Airplane Group announced today.
 A letter sent to airlines by the Boeing Commercial Airplane Group was prompted by recent speculation about whether air passengers could become ill from recirculated air. Most currently produced jetliners combine fresh and recirculated air to ventilate the passenger cabin.
 "We want to reassure airlines and the traveling public that the cabin air systems in Boeing jetliners utilize the best current technology and provide among the safest, most comfortable passenger environments available," said Ken Waters, a research engineer who has specialized in the cabin environment over a 27-year Boeing career.
 Current-model Boeing jetliners typically provide the passenger cabin with about 50 percent fresh outside air and 50 percent recirculated and filtered
air. Waters noted that the 50 percent fresh air content is higher than that often found in office buildings, homes, buses and trains. "During peak heating and cooling periods, office buildings provide as little as 20 percent fresh air and still meet applicable regulations," he said. "And keep in mind that the outside air at ground level is generally not as clean as that in which an airplane flies at cruise altitude."
 He also pointed out that airplane ventilation systems operate continuously during flight, and that the total air flow results in 20 to 30 air changes an hour in Boeing jetliners depending on model. The fresh air portion alone will completely change the cabin air volume 10 to 15 times an hour.
 Waters underscored several key points noted in the letter sent to airlines:
 -- The possibility of disease transmission through air recirculation is highly unlikely. All current Boeing jetliners are equipped with high-efficiency particulate air (HEPA) filters that remove microscopic particles such as bacteria and viruses from the recirculated air. The medical community uses the same type of filters to keep the air clean in hospitals. Laboratory analysis has confirmed the effectiveness of HEPA filters removed from in-service Boeing jetliners.
 -- Concerns about harmful amounts of volatile organic compounds (VOCs) from furnishing, disinfecting or cleaning the passenger cabin do not stand up to scientific evidence. Air samples gathered by Boeing from revenue flights were turned over to a university laboratory for analysis. Only slight traces of VOCs were detected, and the amounts were so low that they could not be quantified.
 -- Carbon dioxide levels in jetliners are well within accepted health and safety standards. For example, the American Conference of Governmental Industrial Hygienists suggests a limit of 5,000 parts per million (ppm). A U.S. government study showed an average of 1,500 ppm in a random selection of smoking and nonsmoking flights.
 -- Based on studies to date, it is unlikely that cabin air causes such conditions as fatigue, headache, nausea or respiratory problems. It is more likely that these conditions are caused by the complex interactions of such factors as the individual's health, jet lag, alcohol consumption, motion sickness, low humidity and cabin altitude effects, among other factors. Boeing continues to support studies of these interactions.
 -- The U.S. Department of Transportation in 1989 funded a study to determine pollution levels in airliner cabins. The levels of bacteria and fungi were found to be below what is generally considered to pose a health risk. The levels measured were similar to, or lower than, those encountered in normal indoor environments.
 Outside air delivered to jetliner cabins is known as "bleed air," which is drawn from the compressor stages in the core of the jet engine and then cooled in air conditioning packs. On older jetliners, powered by straight jet or low-bypass-ratio engines, the bleed system provided the cabin with 100 percent outside air with only a modest impact on fuel economy. By today's standards, however, the engines themselves were noisy, emitted higher levels of pollutants and were much less fuel-efficient.
 On newer aircraft, which are equipped with quieter, cleaner-burning high-bypass-ratio fan engines, fuel efficiency would be lowered appreciably if the bleed system supplied all of the cabin air. Large-diameter fans, driven by the engine core, serve to multiply the overall thrust level of this engine type. For every pound of thrust extracted from the core in the form of bleed air, fan thrust is reduced by an even greater amount, which requires additional fuel and increases atmospheric pollutants.
 According to Waters, combining 50 percent bleed air with 50 percent recirculated air maintains good fuel efficiency while still providing more than ample fresh air. He said the fresh-air portion alone contains far more oxygen than the human body can use.
 "There are several advantages to the current design of the cabin air system besides improved fuel efficiency," he pointed out. "These include an increased humidity level in the extremely dry cabin environment, reduced potential for exposure to ozone at cruise altitude and reduced ingestion of exhaust and other pollutants on taxiways."
 Waters added that the overall quality of the combined fresh and recirculated air in Boeing airplanes meets or exceeds all regulatory requirements and aerospace industry-recognized health and safety guidelines for cabin air.
 "We'll keep looking at new technologies and new ideas for the cabin environment," he said. "Meantime, we've offered to cooperate fully with the U.S. Government in studies of cabin air quality, just as we have in the past."
 -0- 7/29/93
 /CONTACT: Dick Schleh of Boeing Commercial Airplane Group, 206-234-9332/

CO: Boeing Commercial Airplane Group ST: Washington IN: AIR SU:

SB -- SE007 -- 7251 07/29/93 13:27 EDT
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Publication:PR Newswire
Date:Jul 29, 1993

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