The Fokker F28 can be de-iced with engines running, but this was not permitted by the Air Ontario manuals.
The Wikipedia article does not list a source for their claim:
the Fokker F28 aircraft is never supposed to be de-iced while the engines are running because of a risk of toxic fumes entering the cabin of the aircraft
One can however find all details ...
Tip: accident investigation reports cover the system controls related to an accident. The one in question is here (ntsb.gov), from which:
According to the March 20, 1994, edition of FedEx’s DC-10 Flight Manual, page 8-2-2/8-2-3:
Cabin pressure is controlled and maintained by metered release of conditioned air in either an AUTO, SEMI-AUTO, or ...