These unpleasant smells are often described as being like chemicals, burning, faeces, rotting flesh, mold. For some people they appear in response to specific odors, and for others they can be triggered by virtually any smell.
Parosmia can range from mild to severe, and can be an incredibly debilitating and depressing experience for sufferers.” -https://www.fifthsense.org.uk/parosmia-and-phantosmia/