Pet urine damage with discolouration and odour to wool carpets and rugs.
Urine stains go from an acid stain when fresh, to an alkaline stain when dry. The alkalinity causes the the chemical bond of most dyes in wool carpets to change and the fibres suffer colour loss or darkening depending upon the urine strength and volume. In wool this is usually irreversible once the urine is dry, removal in the wet state is more successful.
Urine odour is caused by the bacteria present in the urine and can strengthen as it dries. As cat urine is more concentrated than dog urine it usually has a higher bacteria level and odour. Odour removal from carpets may require the replacement of the underlay and treatment of sub-floor area. In rugs it will have concentrated in the backing and may only improve through full immersion cleaning.

Pet urine damage with discolouration and odour to synthetic fibre carpets and rugs.
Again, urine stains go from an acid stain when fresh, to an alkaline stain when dry. Unlike wool carpets the carpet fibres may darken depending upon the urine strength and volume but as it cannot be absorbed by most synthetic fibres successful removal is quite high.
Urine odour in synthetic carpets is similar to wool and will require the same process for removal.