FLIGHT SAFETY SAFE-SKY: Contaminated cabin air:
The cabin air in modern commercial aircraft has been supplied unchanged since the 1960s with so-called ‘Bleed Air’ from the engines. The dispensing air is used to maintain the necessary pressure booths, ie the oxygen supply to the passengers and the aircraft crew.
This “bleed air” is directly discharged from the engines and flows unfiltered into the aircraft cabin.
In the case of the heavy loads occurring on engines, it can not be guaranteed that all seals fulfill their tasks to 100 percent. In addition, some seals are designed to allow oil to pass continuously in small quantities to function properly. In this way, equipment such as high-alloyed engine oils and aggressive hydraulic fluids enter the pilot air and, consequently, the air in the cabin. (source © Flight Safety Safe-sky)
image credits © Haisam Hussein/ Safe Sky