Truck mounted hot water extraction cleaning is system of choice for the majority of carpet cleans . This is the only system recommended for all carpet types, high pressure cleaning solution combined with very high vacuum flow results in spectacular results combined with fast drying times.

The machine stays outside, reducing noise and disruption in your home or office.

Used for upholstery cleaning and in situations where access to the property does not allow me to use the truckmount for carpet cleaning.

The Ashbys Ninja HWE machine is one of the most powerful electric machines, with twin vacuums and a high pressure solution pump 

This system is used as a low moisture maintenance cleaning system.
The carpet is sprayed with a detergent solution an buffed with a rotary cotton pad.  I would only use this system on low profile or carpet tile carpet as an interim or maintenance clean. Or if drying speed rather than cleaning effectiveness was the prime concern, It does not remove the soil as effectively as hot water extraction, but drying times are usually less than an hour.  Chem-Dry, Texatherm and Dry Fusion all use variations on this theme.  Bonnet cleaning should NEVER be used on loop construction wool carpets