ALTHOUGH REGULAR VACUUMING CAN remove most of the noticeable soil from your carpet, nasties such as pollen, bacteria and dust mites will remain, invisible to the naked eye. Deep-down dirt will wear at the fibre of your carpet and shorten its life, not to mention look unsightly. The two most accepted professional methods of cleaning fitted wall-to-wall carpeting are by wet application (known as steam cleaning or hot water extraction), or by shampooing (also known as dry application) using foam made from chemicals, powders or solvents. Steam cleaning does not involve steam. Instead, hot water is mixed with a cleaning agent within a high-pressure machine, which pumps the mixture through a cleaning tool similar to a vacuum head, producing a deep cleansing process that breaks down the embedded dirt. The dirty solution is sucked back and kept in a holding tank for disposal later. Correct disposal is necessary through a sanitary drain, toilet or proper waste facility; solutions should not be dumped in gutters, gardens or storm-water drains. It is important not to use detergents that are too strong or too alkaline because they may damage the carpet, especially if it is woollen. Care must also be taken not to over-wet the fibre because this can cause shrinkage. If there is any question about the proper cleaning solution to use, contact the carpet manufacturer. Heavily soiled areas should be treated with a pre-spotter before extraction. A popular brand is Viper, available from the store of the same name in Chai Wan (5B Cheung Lee Industrial Building, 9 Cheung Lee Street, tel: 2520 0736) for about $60 for 4.5 litres. Prolonged dampness can promote growth of mildew and bacteria, so dry the carpets as quickly as possible using fans or dehumidifiers. This is especially important during summer months. 'Dry' application involves making a carpet shampoo solution into a cleansing foam, which is then massaged into the carpet and later removed by vacuuming. This is not a popular method because many people believe wet application gives a more thorough clean. 'Dry application is something hotels would choose because it is quiet,' says Greg Andersson of Tip Top Carpet Care (tel: 2834 4545). 'It doesn't generate any noise, but it's not that effective. If you really want to clean the carpet you need to use hot-water extraction.' Professional carpet cleaners in Hong Kong, including Tip Top, Viking (tel: 2556 9553) and ChemDry (tel: 2127 7118), estimate a charge of $1.50 to $1.80 a square foot for the hot-water extraction method. It takes two workers about three hours to clean a flat of 1,000 sq ft, and most carpets are ready to walk on in a couple of hours. Wool carpets retain more water and take longer to dry, while synthetic pile or blended carpets dry more quickly. Mishaps are inevitable in any home and the key to preventing an accidental spill from becoming a permanent stain is a swift response. Tips for dealing with common household carpet spills include: wine - pour salt or any equally absorbent powder onto it immediately; dog or cat urine - pour on a solution of one-third vinegar, two-thirds water to break it down; fruit juice - add cold water mixed with normal shampoo or a laundry liquid designed for woollens. Avoid using household spot cleaners to fix a spill, says Andersson, because this can leave a worse stain or bleach the carpet.