Building service contractors (BSCs) providing their customers with carpet cleaning services should know that there are at least four carpet "conditions" they may run into when maintaining carpets in a commercial facility.
Fortunately, most of these can be corrected if the BSC is properly trained.
According to Bob Abrams, the Carpet Care product manager for Nilfisk-Advance commercial business, makers of U.S. Products brand professional carpet extractors, these four conditions are the following:

Rapid resoiling: This often occurs after cleaning carpets using an interim carpet cleaning method such as bonnet cleaning; either the soils were not thoroughly removed in the cleaning process or chemical residue was left in the carpet.

Solution: Re-clean the area using an extractor with a heating element; an extractor that heats the water/cleaning solution to 212 degrees (F) can improve the effectiveness of cleaning chemicals and remove most chemical residue as well.
Bulges, buckles, or ripples: This can happen if too much moisture is left in the carpet after cleaning but is usually the result of improper carpet installation; if it's a glue-down carpet, it may be the result of adhesive failure.
Solution: If there is too much moisture buildup, re-extract the carpet placing much more emphasis on moisture removal. If the problem persists, installers may be needed to re-stretch the carpet until the bulges, buckles, and ripples disappear.

Tears and rips: Over time, especially in heavily trafficked areas, tears and rips can develop in carpets. Additionally, edges may come loose or seams may open.
Solution: With proper training, most of these issues can be repaired; however, BSCs are advised to "not learn on the job."
Mold: Mold can develop in carpets as a result of exterior moisture intrusion or slow water leaks from pipes in walls or near the subfloor; it can also result from not thoroughly extracting moisture from the carpet when cleaning.
Solution: The best thing to do is nothing. Disturbing mold may cause it to become airborne, turning it into a health hazard. Unless trained on proper mold removal, this should be handled by a trained professional.