Well, the truth is, there may be nothing to worry about at all. But, particularly if your home is older, or if you're experiencing an unusually high incidence of allergy, cold or flu-like symptoms, a good duct cleaning could be all the "medicine" you need.

Here's a checklist of things to consider BEFORE you have your ductwork cleaned:

1. Before deciding to have your ducts cleaned, learn as much as possible about air duct cleaning.
2. If you suspect an indoor air quality problem in your home, consider other possible sources of indoor air pollution.
3. Have your air ducts cleaned if they have deposits of dust or debris or are visibly contaminated with extensive mold growth, fungus or pests.
4. Check references of your service provider.
5. Ask your service provider to show you any mold or other contamination they say is present. Use your own judgment and common sense in evaluating apparent mold growth or get confirmation from a laboratory.
6. Insist that your service provide give you complete and knowledgeable answers to your questions.
7. Find out if your ducts are constructed of sheet metal, flex duct, fiberglass duct board, or lined with fiberglass. The methods of cleaning vary depending on the type of duct being cleaned. Keep in mind that a combination of these elements may be present.
8. Allow biocides to be applied to your ducts only if it is necessary to control mold growth. Make sure that the product will be applied strictly according to label directions.
9. Commit yourself to preventative maintenance including regular filter changes and yearly inspections of your heating and cooling system.