‘It is not the task of passengers and crew to prove that engine oils and hydraulic fluids as used today are dangerous. Just on the contrary, INDUSTRY HAS TO PROVE THAT FLUIDS ARE SAFE BEFORE THEY INTEND TO USE THEM, because standards have been agreed already long time ago, not to use bleed air on transport aircraft.’ - Professor Dieter Sholz 27/04/17. http://www.fzt.haw-hamburg.de/pers/Scholz/dglr/hh/text_2017_04_27_AircraftCabinAir.pdf