Will Fizzion work on a carpet that has been shampooed or chemically treated in the past ?

Yes.  Fizzion does not contain enzymes so its performance will not be compromised by any residues or cleaners used in previous treatments.  If there is any residue on the surface from previous cleaners, it is best to wipe that away with warm water first, before applying Fizzion.  Additionally, Fizzion’s performance, unlike enzymatic cleaners, is not heat sensitive therefore it can be used right before you steam clean without issue.