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Breathe easy?

Yes you can, says Mario Pierobon, thanks to research that puts data before speculation


In recent times there has been public concern in Europe about aircraft cabin air purportedly being of substandard quality. These concerns have escalated following sensational reporting of cabin ‘fume’ and ‘smell’ incidents. Thanks to data collection and analysis efforts undertaken within the aviation industry, scientific evidence has emerged that cabin air quality is in fact very high and there is no threat to health as a result of exposure to it. Earlier in the year EASA had published a study commissioned with the aim of gaining hard scientific facts about cabin air quality on board aircraft for commercial operation. The cabin air quality measurement campaign study was conducted by a consortium of the Fraunhofer Institute for  Toxicology and Experimental Medicine and the Hannover Medical School.

The Lufthansa Group has been actively investigating olfactory incidents in aircraft for several years. This included an intensive and cross-disciplinary investigation into whether these incidents could cause a health risk to passengers and crew members. Lufthansa has so far invested more than €1 million in large-scale projects as part of its effort to get to the bottom of these incidents. Together with other airlines Lufthansa had measurements taken aboard its flights as part of the cabin air quality study commissioned by EASA.

The cabin air of most large transport aircraft is fed by air tapped from low- and high-pressure parts of the engines (bleed air) and, on the ground, from the auxiliary power unit (APU). There is no filtration unit to remove particles or volatile organic compounds (VOC) from the engine bleed air before it enters the cabin, but most aircraft are equipped with High Efficiency Particulate Absorption-Filter systems (HEPA), used to filter recirculated air, which is approximately 40-60% recycled. Ventilation in aircraft cabins is very efficient, typically air-exchange rate in aircraft is circulated more than 20 times per hour. Depending on the type of aircraft, there are differences in the distribution of bleed air. Certain areas, for example, the cockpit, can be provided with 100% bleed air (such as in the 757-300) or with a mix of bleed air and recirculated air (such as in the A380), explains the EASA report.

‘In general, the indoor environment of aircraft is a special issue in the view of health and safety. In cruise flights of commercial aircraft, cabin air is characterised by very low humidity and reduced air pressure (typically equivalent to approximately 2,500m in cruise). In comparison to other indoor air environments such as dwellings or classrooms in schools, aircraft have a high density of occupants and a high load of furnishings. To ensure suitable air quality, the pressurised cabin is operated with very high air exchange rates (~ 15-35-h). Other physical factors potentially affecting the well-being of crew and passengers in aircraft are noise, vibration and radiation,’ the report notes.

For decades, complaints have been raised in Europe regarding air quality in commercial aircraft, reinforced through various health complaints from flight personnel, and occasionally passengers. The report indicates that these health concerns have been linked with potentially acute neurotoxicity and other, mostly non-specific symptoms following a so-called smell/fume event. The overall objective of the study commissioned by EASA was to determine if there are contaminants in cabin air which represent a safety and/or a potential long- or short-term health risk. The investigations paid special attention to possible bleed air contaminants from engine oil, assuming that there are minor releases of engine oil into cabin air inlets especially when there are changes in engine thrust settings during flight.

During the EASA-commissioned study inflight measurements were conducted on commercial flights after defining adequate and reliable air contaminant-measurement methods for cockpit and passenger cabin areas. In total, 69 flights were measured between July 2015 and June 2016 on eight types of aircraft/engine configurations. This included 61 flights on aircraft equipped with engine bleed air systems, and eight flights on the Boeing 787 aircraft, which is equipped with electrical compressors, making up a ‘bleed-free’ system.

As part of Lufthansa’s own study 108 flights were tested from April 2013 to May 2015 on both long- and short-haul flights: 64 flights were with 11 different Airbus A380s whereas 44 were with 15 different Airbus A321s.


There were special measurement kits flying on board the aircraft that were part of the study sample, able to detect 200 substances in cabin air. The kit was developed by the Hannover Medical School and Lufthansa Technik.
Kirsten Winter, Project Leader of Cabin Air Quality at Lufthansa Technik, notes that: “suitable battery-powered pumps were used to take air samples for interior air measurements and workplace measurements. The various sampling equipment (depending on the substance being investigated) were then replaced in accordance with the scientists’ instructions. Samples were taken in various phases of flight. Climate data loggers recorded temperature, air pressure and relative humidity. Continuous VOC, CO, CO2 and O3 measurements were conducted with a GrayWolf Sensing Solutions device. The measurement kit contains all necessary devices in a suitable case, ensuring simple use in daily operations”.

The samples collected by the kit are then examined in the laboratory using standard methods. The kit includes a data logger that constantly records all climate data, such as temperature, air pressure and humidity, while an aerosol spectrometer measures dust content. In total, over 150 VOCs, an additional 15 aldehydes – such as formaldehyde, acetaldehyde and hexanaldehyde – and 19 organophosphates such as tricresyl phosphates (TCP) are monitored. Screening analysis is also carried out to identify unknown substances in cabin air. The same type of equipment was used as part of the EASA study, which also took measurements in the cockpit. >>

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