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FORUMA MONTHLY NEWSLETTER FROM BOEING
COMMERCIAL AIRPLANES GROUP October, 1999 SETTING THE RECORD
STRAIGHT – The Other
Side of the Story: Cabin Air
Quality Well Within Standards, Studies Say A couple of months
ago, a leading British paper carried an article on commercial aviation
containing the following categorical statement: “Cabin air causes
headaches and drowsiness.” When the
reporter was asked for the data supporting the statement of “fact,” his
response was immediate and to the point. “There is none,” he said.
“That's just the way I feel.” Interesting
journalistic standards aside, the subject of cabin air is frequently
the subject of discussion in various venues, but nowhere is it examined
more regularly and thoroughly than at Boeing for one simple reason: it
relates to the health and safety of passengers. Boeing is committed to
providing a safe, healthful and comfortable environment for passengers
and crews. That is why Boeing
in 1994 asked the American Society of Heating, Refrigeration and Air
Conditioning Engineers (ASHRAE) to convene all the interested parties
to establish a scientifically based air quality standard for aircraft.
The goal was to replace the misinformation in the cabin air quality
issue with a standard based on scientific understanding. Current Airplane
Design Our airplanes
typically provide ventilation of 13 to 20 cubic feet per minute (cfm)
of air per occupant. Outside air typically makes up half of the total
air circulation – 6.5 to 10 cfm – while the remaining air is highly
filtered recirculated air. The filtration systems used on most Boeing
products are High Efficiency Particulate Air Filters (HEPA-type),
similar to that used in hospital operating rooms. The systems provide
essentially particle-free air. Results of Air
Quality Studies In the last decade,
there have been 10 focused studies of cabin air quality by credible
organizations such as the U.S. Department of Transportation, Air
Transport Association, Harvard University, ASHRAE and others. The
limited number of flights monitored in these studies have not shown
evidence that the passenger cabin air is polluted or even substandard.
The studies show that concentrations of bacteria and fungal
contaminants, respirable particulates and volatile organic compounds
are relatively low in commercial airplanes. The microbial levels, for
example, in an airplane cabin are typically lower than those in a home,
the airport terminal or the office buildings in which we work. Aerospace Medical Association (AsMA) Special
Committee Report on Cabin Air Quality (Thibeault, MD, 1997) states “The
so-called problem of cabin air quality is most likely multifactorial
(hypoxia, decreased barometric pressure, crowding, inactivity,
temperature control, jet lag, noise, three-dimensional motion, fear,
stress, individual health, alcohol consumption, etc.), and we need to
look at all possible causes before discarding any.” Boeing acknowledges
that passengers and crew do sometimes have headaches, dizziness, nausea
and fatigue during flight and that this is likely caused by a multitude
of contributing factors. Continued
Research Effort For the past
several years, Boeing has been actively involved in cabin
environment-related research conducted by ASHRAE and in our own
internal efforts with select airlines. We are also actively involved in
the development of an ASHRAE air quality standard for aircraft based on
the science available today. We are in the final
stages of a two-year Cabin Environment Program effort which provides
Boeing a foundation of knowledge to guide efforts to improve the cabin
environment. ASHRAE Standard
on Ventilation A key aspect of the
proposed ASHRAE ventilation standard for air quality is a performance
standard for addressing the nature of cabin air quality. The proposed
ASHRAE standards specify air quality comfort and health parameters for
gaseous and particulate contaminants as well as provide comfort
criteria such as temperature, humidity and cabin pressure that meet or
exceed accepted health standards. Filtration requirements are also
specified to ensure effective filtration of recirculated air. However,
one of several proposals put forth recently included a call for
increased ventilation which would drive relative humidity below five
percent, and could likely increase reported health symptoms. Recent studies on
passenger and flight attendant comfort show that humidity-related
symptoms of dry, irritated eyes and dry or stuffy nose are the
predominant health-related concerns on long flights. As a result, cabin
humidity levels are an important factor in addressing the comfort
issue. Current aircraft typically operate at the 10-15 percent relative
humidity range. The cabin relative humidity is dependent on people
being the main moisture source through perspiration and respiration and
the total outside air flow rate. Increasing the level of outside air
(which is very dry at cruise altitudes) would reduce the relative
humidity in the cabin and could decrease comfort. This is one
illustration of how a well-intentioned desire to improve the cabin
environment may yield unintended consequences if not thoroughly
understood. Summary Providing a safe,
healthful and comfortable environment for airplane passengers and crew
requires a balanced look at all the major factors – from air quality
parameters to ventilation rates to individual health and work – all of
which can have significant effect. Boeing is committed to working with
airlines, passenger and crew representatives, medical professionals and
other experts with the aim of ensuring a suitable air travel
environment. http://www.boeing.com/commercial/cabinair/ Copyright © Boeing. All rights reserved.
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