Last I checked their labels, most powdered carpet deodorizers used by consumers contain primarily corn starch (a humectant), a little alcohol and fragrance.  

The problem with these powdered deodorizers is that they are very fine and sift to the base of pile yarns very quickly, if vacuuming isn't done slowly and meticulously - which consumers are reluctant to do. 

The surprise waiting for the carpet cleaner is that the build-up of powder can't be seen during the estimating process before cleaning, unless pile yarns are separated and residue on the primary backing is viewed with a magnifier.  When not anticipated, cleaning progresses normally, but, during drying, the deodorizer powder residue wicks to the tips of pile yarns causing a white appearance, which consumers may interpret as color loss – “You used bleach on my carpet!”  

Repeated vacuuming (often by hand across the entire affected area) and slow, careful cleaning using HWE (often multiple times) is the way ultimately to get rid of this residue.  

Bottom line, consumers shouldn't be using these products since they have only a temporary impact on carpet odor and virtually no sanitizing or disinfecting properties.  They are not EPA-registered.  And the down side is a gradual and almost inevitable buildup of residue that must be dealt with at a future date.  

Certainly, the unsuspecting homeowner is a victim, but that extends to the cleaner as well.  Of course, the cleaner has nothing to do with causing the problem, it’s just that the last one who touches the carpet . . . well, you get the idea.  

If questions remain, don’t hesitate to write.