In some cases, the fibers in the carpets fade or undergo color changes. This may be observed in either a small area of the carpet or only in certain colors in the carpet.

Cause
Dyes exhibit color changes due to many causes: chemical reactions with atmospheric gases, sunlight or chemicals (shampoo, chemical finishes). These changes are usually caused by the chemical changes in dyes that may not be reversible. Most of these chemical reactions are accelerated by heat, sunlight, humidity and the presence of certain chemicals like ozone, oxides of sulfur and nitrogen etc.

Treatment
When this discoloration occurs due to an alkaline dye's reaction to alkaline solutions like ammonia-based cleaning agents, it can be reversed by treatment with treatment with diluted acetic acid. In the opposite scenario, acid dyes react with acidic chemicals and the consequent discoloration can be reversed by treating the discolored fibers with diluted ammonia. But in cases where the reaction occurs under the influence of strong acids or alkalies, the resulting chemical reaction is irreversible. Fading due to exposure to sunlight is usually irreversible and here precaution is often easier than cure. To protect your valuable rugs, make sure that they sre not exposed to strong/direct sunlight. Use of window blinds and ultra-violet (UV)ray-proof glass also prevents color loss due to sunlight.

NoteIn many cases` this discoloration is hidden by soils and is more apparent after cleaning.