Environmental Engineering Reference
In-Depth Information
A review of the concentrations of organic compounds in cabin air has indicated
that contaminant levels are similar to those that exist in residential and ofice
buildings (Nagda and Rector
2003
). However, there were two exceptions. First,
levels of ethanol and acetone - indicators of bioefluents and chemicals from con-
sumer products - were higher in aircraft air than in home or ofice environments, or
in other transportation modes; second, levels of certain chlorinated hydrocarbons
and fuel-related contaminants were higher in residential/ofice buildings than in
aircraft air. The levels of the
m
- and/or
p
-xylenes tend to be lower in aircraft.
Although cabin air is iltered through adsorbents, prior to recirculation, to remove
volatile organic compounds and odor, such devices are not installed in all aircraft
and may not be capable of removing all pollutants. Therefore, the photocatalytic air
iltering approach was developed and this approach seems to be a promising method
to resolve odor problems in aircraft (Ginestet et al.
2005
). This photocatalytic unit
consists of four UV lamps sandwiched between two interchangeable titanium diox-
ide-coated panels and is designed to oxidize volatile organic compounds. The over-
all eficiency of the catalytic unit was dependent upon the chemical characteristics
of the compounds that were used to challenge the unit. The compounds used were
toluene, ethanol, and acetone. The tested unit did not fully remove toluene, since the
unit relies on oxidation to remove substances, and toluene is the most dificult com-
pound to be oxidized. Moreover, although the tested prototype unit is able to par-
tially oxidize volatile organic compounds, partial oxidation of some toxic
intermediate chemical reaction products may result in the production of intermedi-
ates such as formaldehyde and acetaldehyde.
High concentrations of ozone in cabin air can lead to upper respiratory problems,
and inhaling the high levels of CO
2
that may occur in cabin air may produce hyper-
ventilation (Bergau
1999
). Breathing cabin air may also cause the mucous mem-
branes of the respiratory tract to dry out because of the extremely low humidity of
cabin air. In a 2000 study by Backman and Haghighat (
2000
), air quality in 15 dif-
ferent aircraft was measured at different times and altitudes. High CO
2
concentra-
tions and low humidity levels were found in the Airbus 320 aircraft. The highest
humidity level was found in the DC-9 aircraft and the lowest CO
2
concentration was
analyzed in the Boeing 767 aircraft. The authors concluded that poor air quality
may cause intolerance to contact lenses, and dry eyes, and may be a health hazard
to both passengers and crew members. In the US Air Force C-5 aircraft cabin air,
carbon monoxide (CO) and CO
2
concentrations were found to be well below health
effect thresholds, whereas the lowest level of relative humidity found was 3%, and
ozone existed at relatively low concentrations (Hetrick et al.
2000
). The inluence of
ozone on self-evaluation of symptoms in a simulated aircraft cabin indicated that air
quality, as measured by the presence or absence of 12 symptoms (e.g., eye and nasal
irritation, lip and skin dryness, headache, dizziness, mental tension, and claustro-
phobia), was established to be signiicantly worse (
p
< 0.05) for the 60-80 ppb ozone
atmosphere (“ozone” condition), compared to the <2 ppb ozone atmosphere (“no
ozone” condition) (Strom-Tejsen et al.
2008
).
During intercontinental lights, CO
2
levels were below 1,000 ppm in 97% of the
cases and humidity was very low (mean 5%) (Lindgren et al.
2000
). Low humidity
Search WWH ::
Custom Search