Vacuum cleaners have been on the market for a century and common in ordinary homes for about half that long. Yet recently many homeowners have come to see the wisdom in owning something more powerful: a carpet cleaning machine.

Technically, yes, a vacuum cleaner is a "carpet cleaning machine" in that it's a machine that cleans carpets. What we're talking about here are heavy-duty devices that clean a carpet more deeply and thoroughly than an ordinary vacuum, giving not just a superficial clean but a complete, deep-down cleansing of the actual carpet fibers.

Where a vacuum cleaner simply uses a roller to dislodge dirt and suction to suck it up, a carpet cleaner usually uses a cleaning solution of some kind to really cleanse the carpet fibers.

Other machines, known as steam cleaners, use steam to achieve the same result.

The average home may not need these devices except occasionally, maybe for a three-times-a-year deep cleaning. As such, they can often be rented rather than purchased, and they are easy for an ordinary person to use.

High-traffic areas, however, such as businesses and homes that see a lot of guests, may benefit from owning a carpet cleaning machine. In fact, some vacuum cleaner manufacturers are starting to make cleaners, too, pricing them reasonably and presenting them as an alternative to an ordinary vacuum cleaner. Why get the carpet only nominally clean when you can deep-clean it every time?

Before buying such a device, you should make sure your carpet can handle it. Some carpeting, especially if it is older, may not stand up to repeated deep-cleanings. Most modern fibers can take it, but it's best to be sure.

Ensure also that the carpet cleaner you're considering will suit your home's particular needs. Is it heavy? Will you have to lug it up stairs? What kind of attachments and hoses does it have? Will it work on thin, flat carpets as well as deep shags? Know ahead of time what your needs are so you can make a wise purchase.