Check their clothing, plants, pictures, and even chairs or storage boxes/drawers etc.  Of course there might even be a leaky capacitor, ballast,  or something of the sort with a heated liquid chemical agent leaking-?

 

Years ago my wife, trained as an industrial hygienist, helped investigate an "untenable" odor in the brand new office in a brand new building - of one of our more prominent heads (the chair) of a specific medical department.  Days of investigational snooping went by - along with the brand new carpeting being pulled up and replaced, the air supply ducts being manually cleaned (expensive), the chairs, desks and walls being closely examined - and a number of other solutions to the problem being tried - all WITHOUT apparent success. 



She visited the faculty member to update him on all the work that had been done over the past few weeks and he said it was not enough - because the odor continued and he was unable to work in that environment.  During the course of this visit she asked the faculty member about a couple "personal" items in the new office - and whether they had been added before or after the smell started-



One item she observed was a "LARGE" plant that had been =E2=80=98a move-in gift from the "chair's" wife=E2=80™.  It looked like it had recently flowered - and when my wife sniffed it she was surprised enough that she winced at the smell - so she asked the faculty member to come over to the plant and then queried - was this the objectionable smell?



The response was "yes" - and the plant was removed=E2=80=A6

 

Good luck-

 

                 jp