**Conflict of interest**

*Indoor Environment and Health*

dollars in 2012 [39].

**4. Conclusions**

contamination.

on most flights that were tracked:

1. cabin altitude average remained below 1000 ft,

2.CO2 levels ranged between 900 and 1700 ppm,

and dropped to 10–25% as flight progressed, and

5. sound level was approximately 86 dBA.

3. cabin temperature ranged between 22 and 29°C (71.6–84.2 F),

downloading to a central database. Testing was done onboard number of actual flights, approximately 15 flights, and the following were some of the observations

4. relative humidity ranged between 35 and 50% at the beginning of the flights

Other studies investigated air fume, smoke and other related incidents on board actual flights and the associated incurred costs that can result due to delays and cancellations in corresponding flights. Shehadi et al. [40] reviewed databases from NASA, US Federal Aviation Administration (FAA), US Department of Transportation (DoT) and analyzed incidents on 33 aircraft models and sub-models. The study considered the different engines' and auxiliary power units' (APU) makes and models. The analysis showed that thousands of flights would need to be monitored to determine the root cause/source for a reported incident. Although the cost of the thought study might be high, but the associated costs due to delays and cancellations of flight due to such incidents can be approximately \$32,000– \$47,000 per aviation incident totaling approximately \$4.5-million–\$7-million US

A review for studies done at the Airliner Cabin Environment Research Lab (ACERL) housed at Kansas State University was done in this chapter. Studies were categorized as per the method of study such as PIV, particle dispersion, CFD, tracer gas, and bleed air. The studies investigated airflow and turbulence characteristics in various airline cabin structures such as a generic room, Boeing 767 and 737 mockup cabins, actual aircraft, and a bleed air simulator. The objective of this chapter is to provide a database of experimental and computational study references that can be used to validate further computational investigation which in turn would help in designing a state-of-art contamination and bacterial sensors to be used on board flights and ultimately would help in improving the quality of air inside airplane cabins. The studies can also help aircraft designers improve the design of the ventilation system in the aircrafts and would provide guidelines for maintenance teams to follow better practice that can prevent previous incidents such as bleed air

Tracer gas and powder particles were used to simulate the dispersion of bacteria and viruses. It was observed, particularly with the longitudinal dispersion, that the various forms of contaminants behave in a similar dispersion manner. However, the relative bacteria concentrations appear to drop off more quickly with distance than those with the tracer gas and solid particles. This might be caused due to the fact that only viable bacteria would be counted during the studies. This might provide bias or incorrect results as some bacteria would be removed by the aircraft ventilation system and others might have become nonviable before they reach the more

**14**

The authors do not have any conflicts of interest.

## **Nomenclature**


*Indoor Environment and Health*
