When considering this question, one should consider the following facts:
Much pollen, bacteria, dust mites and mold, which together with other invisible pollutants, settle in the air ducts, are re-circulated every time the furnace blower is switched on, with serious detrimental affects on allergy sufferers.
Many physicians now expressly recommend air duct cleaning for minimizing the affects of these harmful pests and dirt. The combination of these contaminants and moisture, when found in air duct systems provide ideal breeding grounds for mold, germs, fungi and other harmful microbes, which are harmful to the elderly, children and sufferers of a number of serious diseases.
Notwithstanding the aforementioned, only allow air duct cleaning after you have studied all the facts involved. Use the Internet and information from reliable service providers before making a decision.
There are many other possible causes of indoor air contamination. Only have your air ducts cleaned if they are visibly contaminated with substantial mold growth, pests or vermin, or are clogged with substantial deposits of dust or debris.
Insist that service provider to show you any mold or other biological contamination they say exists and insist on laboratory confirmation of mold growth before making your decision.
Only allow the use of biocides in your home if you have been convinced that they are necessary for decontaminating it and no matter what the product, make sue that no people or household pets are in the home during application.
Make sure the service provider follows the National Air Duct Cleaning Association's (NADCA) standards and, if the ducts are constructed of flex duct, duct board, or lined with fiber glass, the guidelines of the North American Insulation Manufacturers Association (NAIMA).
Steam cleaning and other methods involving moisture should not be used in any kind of air duct work.
Carpets and upholstered furniture are well known preservers of allergens and dust and dirt particles. Regular professional cleaning of these items will ensure that you have a safer, cleaner and healthier home.
A common misconception is that if one wets out carpets and furniture, they will automatically be cleaner.
However, USA Clean Master .com recommend using the dry systems of cleaning your carpets and furniture so that dirt, dust, and other allergens are lifted to the surface and swept away instead of being forced deeper into your carpet by excessive applications of water that cannot be removed or dried out completely.
Excessive wet cleaning with water that cannot be removed completely, can leave areas that act as breeding grounds for mold and bacteria. Often wet cleaning leaves harsh chemical with a high pH residues, which could result in irritation to people and pets.