Environmental Engineering Reference
In-Depth Information
vehicle material, crew metabolism (CO
2
in particular), payload chemicals, and
thermal degradation of materials present in the aircraft (Patterson and Rayman
1996
). Therefore, the protection of the astronauts' health and preventing their per-
formance decrements are crucial. A major need in the space cabin is to establish
maximum allowable concentrations of potentially toxic substances. Such an effort
should be based on the fact that astronauts live in the closed environment of their
space vehicles 24 h a day, for weeks or even months, in comparison to the standard
8-h shift worked by most terrestrial workers. Exposure to microbes in the space
cabin is also of concern because crew members release many bacteria into the envi-
ronment, and exudation of aerosols in a microgravity environment results in drop-
lets being suspended in the atmosphere. Both factors render exposures more likely.
How microgravity affects the immune system of humans has not been well estab-
lished. Therefore, monitoring for microorganisms and toxic substances in the space
vehicle cabin atmosphere is essential. Surveys have shown that the methods and
means of qualitative and quantitative air monitoring on the International Space
Station are currently suficient for air control in emergency situations such as local
ire and toxic leak; moreover, the Station's air quality is regarded to be suited to the
existing standards and crew safety requirements (Pakhomova et al.
2006
).
3.4
Fumes/Smoke in Aircraft Cabins: Analysis and Effects
Pyrolytic products of jet engine oils, hydraulic luids, and/or lubricants may enter
aircraft air by leaking in through ventilation systems (Crane et al.
1983
; Sanders
2007
; van Netten
1999
; van Netten and Leung
2001
). When this occurs, exposures
to them may impose a threat to the operating aircraft and to their occupants (Rayman
and McNaughton
1983
). Smoke/fumes-related incidents are usually caused by bro-
ken engine seals or associated systems that allow smoke and fumes to enter the air
compressor section from where they can contaminate the interior of the aircraft.
Catalytic converters have been used to clean the air (van Netten and Leung
2000
),
but when an oil seal fails, such systems can easily become overloaded, allowing
smoke to enter the cabin. The potential for exposure to thermal breakdown prod-
ucts, including smoke or other toxic gases, may cause performance impairment of
the crew members. Dizziness, nausea, disorientation, blurred vision, tingling in legs
and arms, central nervous system dysfunction, and mucous membrane irritation
have frequently been reported by light crews. Such symptoms are consistent with
exposures to CO and some pyrolysis products, including volatile organic com-
pounds and the organophosphate constituents of the oils and luids, but the involve-
ment of these liquids has not been clearly demonstrated (van Netten
1999
).
Smoke consists of particulate matter and a variety of invisible combustion gases
and vapors that are suspended in the ire environment, resulting from a rapid exo-
thermic chemical chain reaction between a fuel and oxygen (Landrock
1983
; Meyer
1977
; Smyth et al.
1992
; Strahle
1993
). The types of combustion gases produced
depend upon the nature of the chemical constituents of the material being burned.
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