There is only one safe way to clean carpet: thoroughly and on-location without using damaging amounts of liquids.

It's Not the Rotary Method
Here shampoo is scrubbed onto the surface of the carpet using one large or two small brushes. This does a fair job of cleaning the carpet surface, but the deep-down dirt is either untouched or carried deeper into the pile by the shampoo. And this method makes no provision for removal of the shampoo and dirt. The carpet must be vacuumed later in a separate operation.

It's Not the Steam Method
In the first place, no steam is used - probably a good thing since live steam would be disastrous to your good carpet. Actually, the "steam" is only hot water that is sprayed into the carpet. And in most cases, little more than half of the dirt bearing water is extracted from the carpet. The remainder is left and can result in soggy carpet, browning mildew, shrinkage, or damaged backing, padding and floors. Drying time can run up to 24-hours - a long time for any carpet area to be unusable.

It's Not the Rotary/Bonnet Method
Such procedures will brighten the surface but can't remove the dirt deep in the pile. Results: embedded dirt works up quickly to the surface to resoil the carpet.

What Is It? - It's Low Moisture Extraction...