Hi firstclasscleaning,
Welcome back to the forum!
It is generally not recommended to clean your air ducts yourself, as you will not be able to clean the entire length of them without proper equipment. However, if you would like to try to clean a portion of them there are instructions here
http://www.repair-home.com/Do_It_Yourse ... aning.html
A professional duct-cleaning service can do a thorough cleaning of the air ducts in your home or office. It is recommended that you have them professionally cleaned to maintain cleaner air quality, which will reduce mold spores, dust mites, fungi, bacteria and other allergens.
The National Air Duct Cleaners Association offers a lot of good information about the subject here
http://www.nadca.com/consumerinformatio ... sumer.aspx
Good Luck and let me know how it turns out!
Mrs. Clean