Not long ago I cleaned a house in Greensboro, North Carolina. My customer's dogs slept in the hallway every night outside their bed room (because the would shut their bedroom door to keep them out). Like any dog that loves their owners, they would sleep right outside their door. Over time oils from the dog's coat of fur, mud and other dirt built up more and more.
Here's what my company Cardinal Cleaning Systems did to restore their Carpet.
1.) Vacuum the areas from wall to wall. Even the corners and edges (also a second pass with the vacuum never hurts).
2.) Pre-spray all the affected areas.
3.) Let the pre-spray dwell for 10 to 20 minutes.
4.) Spot clean all trouble spots.
5.) Clean the carpet using the Von Schrader LMX (Low Moisture Extraction) System.
The carpets look brand new after this process. My customers were very pleased. Cardinal Cleaning Systems sees this regularly and restores carpets every time.
If you have a similar situation and want to restore you carpet like the pictures above,