Eli5: why is volcanic ash dangerous to aircraft, and yet they can fly through forest fire smoke?

Question

Thank you!

In: 32

Answer 1

Volcanic ash can reach above the troposphere and has silicon in it and can get in an aircraft engine and choke out the oxygen and also wreak havoc on the windows and airframe of the aircraft.

Forest fires are never reach high enough with enough density to cause problems for aircraft and in some places of the world like Indonesia they fly in to heavy areas of smoke without any short term problems.
Aircraft maintenance takes care of long term carbon build up as aircraft engines have to be maintained and replaced on a maintenance based schedule