The Hot Water Extraction (HWE) method, is a method used in chemistry for extraction and for "steam

Steam

Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

 cleaning" (e.g. carpet

Carpet

A carpet is a textile floor covering consisting of an upper layer of "pile" attached to a backing. The pile is generally either made from wool or a manmade fibre such as polypropylene,nylon or polyester and usually consists of twisted tufts which are often heat-treated to maintain their...

s. as listed by the IICRC to be the primary method for cleaning carpets. Residential, and Commercial). The pressurised hot water extraction (PHWE) process uses a combination of high water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 pressure

Pressure

Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 for agitation, and hot water to increase reaction rate.

"Steam Cleaning"

Though commonly called "Steam Cleaning", no actual steam is involved in the HWE cleaning process, apart from steam that may escape incidentally from hot water. When the cleaning solution comes in contact with the carpet/rug, it is anywhere between 120-250 degrees Fahrenheit, according to the heat available from the cleaning unit. For instance, in a modern truck

Truck

A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

-mounted carpet cleaning machine, water can be heated to 300+ degrees (F), but after passing through high pressure steel braided hose

Hose (tubing)

A hose is a hollow tube designed to carry fluids from one location to another. Hoses are also sometimes called pipes , or more generally tubing...

 and several manifold

Manifold

In mathematics , a manifold is a topological space that on a small enough scale resembles the Euclidean space of a specific dimension, called the dimension of the manifold....

s, the water loses much of its heat

Heat

In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

.

The typical cleaning method involves a preconditioning of the soiled surface with an alkaline

Alkalinity

Alkalinity or AT measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution...

 (7 or above on the pH Scale) agent, followed by light agitation with a grooming brush

Brush

A brush is a tool with bristles, wire or other filaments, used for cleaning, grooming hair, make up, painting, surface finishing and for many other purposes. It is one of the most basic and versatile tools known to mankind, and the average household may contain several dozen varieties...

 and appropriate dwell time. Next, the surface

Surface

In mathematics, specifically in topology, a surface is a two-dimensional topological manifold. The most familiar examples are those that arise as the boundaries of solid objects in ordinary three-dimensional Euclidean space R3 — for example, the surface of a ball...

 is passed over several times with a cleaning tool (either manual or automatic) to thoroughly rinse out the preconditioner and, using an acetic acid solution, lower the pH

PH

In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

of the fibres to a neutral state. Finally, the surface is dried sufficiently to avoid any possibility of saturation.