Over the past few decades there has been a fundamental design fault in the majority of aeroplanes used to move people around the world. Cabin air is taken from air that is used to cool the engine. This is cheap because this air has already been warmed and compressed by the jet engines. However it is subject to contamination from the engines particularly if engine design is faulty or if engine seals become worn. Indeed all jet engines leak oils and fumes to a certain extent and these chemicals get in to cabin air. Because jet engines run at such high temperatures, additives are put into oil so they can work better. Therefore depending on the design, the age and the recent service history of the engine, occupants of any aircraft will be more or less poisoned by these fumes.
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