P.U.R.T.® , Pet Urine Removal Treatment, is a revolutionary
  new product specially formulated to eliminate urine odors.
  This product has shown excellent results on even the most
  severe pet or human urine deposits.

Facts You Need to Know About Urine in Fibers:

  Urine causes permanent damage to fibers, decreasing the
  tensile strength and causing light to reflect differently.
  The bleaching properties of urine can result in color loss,
  sometimes it contains ingredients that dye the fibers. Urine
  deposited on carpet does not stay there, it penetrates the
  fibers and contaminates both the backing of the carpet
  and the flooring material below the carpet. Often,
  without your knowing, pets will urinate continually in the
  same general location. Urine odors can permeate from
  the floor, be it cement or wood, from the tack strip, and
  even from the framework of the house behind the walls.
  It takes Nature about five years to decompose the urine
  deposit.

  As urine dries, the liquid evaporates
  but the urine crystals become even
  more concentrated and pungent.
  Some crystals have spikes on them,
  causing them to more firmly attach
  to fibers, much like foxtails or burrs.
  Simple cleaning with any process can not remove this
  deposit. Until recently, there was not a product available
  that was effective at removing urine odors. When P.U.R.T
  contacts the source of the odor, it immediately begins a
  chemical reaction that destroys the urine odor.

How P.U.R.T. Works

1. The source and severity of the odor are determined with a professional cordless black light and moisture probe inspection, then the carpet will be rinsed and extracted with a hot water rinse to remove the bulk of the urine crystals.
2. In worst cases the carpet is pulled back in the suspected areas to reveal the extent of the damage.
3. If necessary, the pad may need to be removed and replaced. Additional costs may apply. 
4. An odor blocking shellac may be applied to the subfloor if determined necessary. Additional fees may apply. 
5. When required, P.U.R.T. will then be applied heavily to the tack strip, the sub floor, the baseboards and the carpet backing. It may be necessary to apply this product heavily enough to dampen all areas affected by the urine. Fees appropriately required for this extensive work.
6. Over the next 24 to 36 hours, the ingredients in P.U.R.T. will react with the urine, and break down the odor causing components.