Cabin environment

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The Airplane Cabin Environment
Issues Pertaining to Flight Attendant Comfort
Elwood H. Hunt and David R. Space

Introduction
conditioning packs located under the wing center section,
The purpose of this paper is to examine some of the
and mixed with an equal quantity of filtered recirculated
conflicting information written recently on the subject of
air. This is shown in figure 1, and istypical of modern
cabin air quality by looking at the perceptions and facts of
generation airplanes. Approximately 20 cubic feet per
the cabin air as they are currently known. In addition,
minute (cfm) of air per passenger is provided, of which half
environmental issues and factors affecting in-flight service
is filtered recirculated air and half is outside air. This results
attendants andtheir comfort are addressed.
in a complete cabin air exchange every two to three minutes
Many articles of late have been written on the subject of
(20 to 30 air changes per hour). The high air exchange rate
cabin air quality, with the presumption that the quality of
is necessary to control temperature gradients, prevent
cabin air is dependent upon its source. That is, the air
stagnant coldareas, maintain air quality and dissipate smoke
reprocessed by nature, outside air, is “clean,” but the air
and odors in the cabin. High outside airflow rates are also
reprocessed by the aircraft environmental control system is
necessary to maintain overall cabin temperature control and
“not clean.” Consequently, since newer model airplanes
cabin pressurization.
reprocess a portion of thecabin air,
the general theme of these articles is
Cabin air ventilation:
that the air supplied to the cabin is of
1 Outside air continuously enters engine where it is compressed.
3 Air from the mixing chamber is then supplied to the
poor quality. The belief is that outside
cabin from overhead outlets on a continuous basis.
It then passes through cooling packs to a mixing chamber.
airventilation is low and the use of
Outside air entering the mixing chamber is mixed with
4 As outside air enters the airplane, it is being
2
recirculation systems supposedly
continuously exhausted.
recirculated air that has been cleaned with high efficiency
filters. The filters are similar to those used in critical
results in a buildup of contaminants,
wards of hospitals. The makeup of air inthe mixing chamber
is approximately 50% outside, 50% recirculated.
spread of disease, insufficient oxygen
for breathing and high carbon dioxide
3
Passenger compartment
levels.
air distribution
Do these articles contain miscon2 Mixing chamber
4
ceptions or facts, or are there other
Outflow valve
factors that are more likely causing
symptoms attributed to air quality?
Such symptoms asfatigue, headaches,
Gasper fan
1
nausea, dizziness, eye and nose
Air-conditioning packs
irritation and respiratory problems
(2 locations)
have been reported on occasion by
flight attendants. Before delving into
Engine
perceptions and facts relevant to cabin
1
2 Recirculation
air quality, a brief discussion of
system (2 locations)
Flight compartment air distribution
Boeing designapproach and philosophy of an airplane’s ventilation
Figure 1. 767 airplane ventilation system
system is in order.
How an Airplane Ventilation System Works
The outside air supplied to the cabin of the 767 airplane
is provided by the engine compressors, cooled by air-

Due to the large quantity of air entering the relatively
small volume of the cabin, as compared to a building,
precisecontrol of the airflow patterns is required to give

1
This paper my be reproduced in its entirety or by complete section without specific permission from The Boeing Company.
However, reproducing less than all of the paper or complete section, or changing the paper in any way, requires prior
written permission from The Boeing Company.

Center
stowage bin

Conditioned air
distribution duct...
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