I would love to offer great advice on chems and such but you need to tell us are we working with wool vs synthetic and is it carpet, or area rug, or upholstery, if its an area rug is it tufted, or woven, if its carpet is it glue direct or over pad, what kind of pad, what kind of backing?? see.. details man. Is it a dog or cat or other animal? What has the customer tried before hand. There is no such thing as a kill all in the decontamination game. And probably most importantly is the pet gone or will they have access to the area again...
If I tried to answer and explain steps to each of these questions, you would have a very long post to read and i would be very late getting home!
Answer a few specifics and somebody will be along shortly to give you a good answer to your specific problem. Otherwise we are shooting blindly from the hip!