Passengers are often surprised to hear that the air they breathe comes from inside the engines.
This sounds unhealthy. Can you explain, why it is not ?
Is bleed air tapped (for cabin pressurization) before or after it comes in contact with fuel inside turbofan engines on passenger airliners ?
And what is the reason for either choice ?
Specifically where is the location in this diagram ? (diagrams in answers would be very welcome)
scope: This question is about the air breathed by humans inside the plane. Q11917 is about de-icing. Neither the question nor the answers in Q11917 deal with the aspect of whether the air would be safely breathable for passengers and crew. This aspect is very well dealt with in the comments and answers below. As such, these questions should remain separate.