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INTRODUCTION

Currently only air temperature and barometric pressure are routinely measured in commercial aircraft cabins. These limited measurements are not sufficient when the environmental control system is not properly working, and they are not intended to be used to detect of monitor air-quality characteristics on commercial aircraft that include ozone, carbon monoxide, carbon dioxide, relative humidity, and fine particulate matter.

Without the presence of appropriate sensors in the aircraft, information on contaminant transport cannot be obtained in a timely fashion. It is speculated that during the Severe Acute Respiratory Syndrome (SARS) outbreak in 2003, 22 passengers may have been infected by SARS on the flight from Hong Kong to Beijing (Olsen et al.2003) due to possible release of the SARS virus from and infected passenger. If a SARS sensor had been available and properly placed in the airplane, it might have provided the SARS release information during the flight so necessary protective measures, such as using oxygen or masks, could have been taken. Furthermore, after the use of the nerve agent sarin to attack the Tokyo subway system in 1995 and the anthrax cases in Florida and Washington, DC, in 2001, there have been fears expressed of possible terrorist attacks by releasing chemical/biological agents in commercial airplanes. It would be beneficial to obtain the release information of chemical/biological agents in advance to protect passengers and crew. Thus, a suitable placement of sensors on commercial airplanes can play a critical role in monitoring cabin air to create a comfortable, healthy, and safe cabin environment for passengers and crew.

Typically, one would place s sensor at the air exhaust in an airliner cabin because the current air distribution system creates a missing condition. The obtained measurement information, while useful, may be difficult to use to find contaminant sources, however (Zhang and Chen 2007a). Because of the dilution of the contaminant due to strong mixing effect, the detection would need very sensitive sensors and long time of exposure. Thus, by the time a contaminant is detected, the whole cabin may have been polluted. Previous research on airborne contaminant transport in a room showed that sensors can detect very different contaminant concentration levels at different locations (Zhai et al. 2003). Zhai et al. (2003) found that an early warning before the contaminant reached an occupant in the room was possible by placing sensors appropriately in the room. Since the room environment is similar to a cabin environment in terms of airflow and contaminant transport characteristics, it is also possible to obtain early warning data from sensors if they are placed in proper locations inside the cabin.