volcanic ash
I fly a Kingair with PT6A engines.
PW have issued a guidance, SIL gen-102 - ENGINE OPERATING IN EUROPEAN AIRSPACE which as I understand it says you can fly in the red but not the black areas provided you undertake extra inspections which for my engine is a 50 hour check and a monthly check.
Maybe you should contact your engine manusfacturer to see if they have issued guidlines.