The organization who write those standards is called IICRC, or the Institute Of Inspection Cleaning & Restoration Certification. Their standard is called IICRC S100 Standards Reference Guide for Professional On-location Cleaning of Installed Textile Floor Covering Materials.
A chart showing strengths and weaknesses can be found here!
Most of the problems that occur from cleaning are due to mistakes made by the technician and/or his failure to comply with the cleaning standards. Problems with defective carpet, faulty equipment, and defective chemicals happen less often.
Five Basic Steps for All Methods of Carpet Cleaning:
The question often arises on which method is the best and the answer to could be likened to 'what is the best automobile.' A better question might be who is the best cleaning technician. A cleaning technician with IICRC CCT, Certification from opinion is a good choice. However, there are some likely inherent difference between methods.
To see what could go wrong after the carpet is cleaned, click here.