Hi Anons, I have a bit of belated research that may be related to the Raleigh Airport event.
The hydraulic fluids on aircraft are usually phosphate esters, the main one being Skydrol which used to be a Monsanto product, but is now supported by Eastman.
https://www.eastman.com/Brands/EAS/Resources/Pages/SDS.aspx
A leak of Skydrol into one of the engines and although phosphate esters are self-extinguishing, given enough energy they will burn and release phosgene.
Bypass air from the engines is used to pressurise the cabin, so anything that gets in the bypass air stream gets fed into the cabin.
When I head about this incident my immediate thought was Skydrol. I worked in the oils and lubricants industry for a very long time so I speak from experience.