Professional carpet cleaners encounter three basic problems with carpets related to the cleaning process-browning, bleeding and static. 
Most browning is characteristic of older carpets. In new carpets the cellulosic materials have not been abused enough to begin breaking down. Browning is also referred to as a colour change. A variety of factors lead to colour change on carpets as a result of the cleaning process. A colour change can be caused by a change in the colour of indicator dye. The carpet dyes actually change colour corresponding to the pH of the chemical carpet cleaners are using.

Other colour change issues arise when soil and vegetable dyes in the fibre loosen up at the time of cleaning and wick to the surface when drying. Trained NCCA trained carpet cleaners are well-aware of the four main factors affecting browning: overwetting, alkalinity, cellulosic Fibers and improper drying and ways of preventing them.

The problem of bleeding occurs during the carpet cleaning or drying when the dyes from one area bleed into another area of different colour. To prevent this from happening professional carpet cleaners test the areas that may be susceptible to bleeding. When placing furniture on damp carpet technicians need to avoid stains from stained legs. Static electricity is another common problem. Most of the new carpets hold down static. Professional carpet cleaners can only apply a chemical that will hold the static temporarily, up to 6 months, to reasonable levels.