Why is it important ?

In most modern large aircraft equipped with turbine engines outside air, used to pressurize and ventilate the cabin, is extracted either from the main engine compressors in flight, or from the Auxiliary Power Unit (APU) on the ground. This so-called bleed air then passes through the air conditioning system of the Environmental Control System before being distributed to both the cabin and cockpit.

The triggering of CAC events may be caused by a variety of sources, either internal or external to the aircraft, for example:

• Ingestion of exhaust gases or fuel vapours by the air conditioning system when the aircraft is on the ground, creating temporary on-board unpleasant odours or smells;
• Contamination of the bleed air by oil and its pyrolysis products as a result of faulty conditions in the engines or APU – notably due to failures of oil seals or bearings, errors or irregularities in engine or APU maintenance procedures;
• Pollution of the cabin air by anti/de-icing fluids or aircraft hydraulic fluid due to system malfunctioning or operational failures.

Although representing a small proportion of these types of events, contaminations by oil or aircraft fluids and their by-products are those that raise the utmost concerns. For this reason this project will focus on oil related contamination. Other types of events, such as smell in cabin (SIC), are beyond the scope of this project.

Over the past two decades, extensive research on both the quality of the cockpit/cabin air and its relation to health effects have been performed worldwide – including some attempts to identify the consequences of CAC events. So far, a causal relation between cabin air contamination and ill-health in aircrew could not be scientifically substantiated. However, the reported effects are the reason for further investigation of potential health implications.

Conscious of the public interest in the issue, its sensitivities and inherent difficulties, the European Commission, supported by EASA and various aviation stakeholders, decided to start a new initiative aimed at collecting additional scientific evidence on which to root more robust policies in this subject area.

The route proposed herein is not merely to re-iterate the disparate approaches of the past, notably in terms of just extending the scale of on-board measurements of air data quality. The aim will be, rather, to attempt to formulate and experiment novel ideas – including e.g. a combination of advanced air monitoring and analysis of controlled experiments aiming towards worst case scenarios, the setting-up of standardised data collection and analysis procedures and protocols – providing best-practice standards for the establishment of future air quality and the use of experimental animal and in vitro models to identify possible neurological adverse effects following exposure to contaminated air samples. The goal will be eventually to produce a robust scientific and experimental baseline towards enabling step-advances on the understanding of the effects of cabin air contamination, regarding its public health implications. This will allow eventually proposing and implementing appropriate mitigation measures should they be deemed necessary.

Fulfilling such a goal calls for a new ecosystem of collaborations between the scientific and the industrial communities at large, to mobilise the multitude of disciplines and expert skills that can make the whole idea feasible. This is reflected by the FACTS consortium, hosting various prominent experts in the areas of air pollution, chemistry, toxicology and aircraft manufacturing.