There is a lot of debate on whether cleaning air ducts regularly is necessary or not. It does stand to reason that air ducts do hold dust, but most people say that it does not hold an unusual amount. The key to deciding whether you really need your air ducts cleaned or not should be based on what you see and the people inside of your home.
If you look down in the vent registers of you home and see a lot of dust build up. It could mean that air is not flowing through it properly. You should also take notice of foreign objects that may have fallen down inside of the ducts. In some cases, mold may also form inside of the ducts and if you see any of that, you need to get it cleaned immediately. The downside is that mold will most likely require a professional touch.
Research has proven that people who have a lot of airborne allergies are worse off if their air conditioning duct work is dirty. This means if you notice your family having a lot of allergies that they never had before or if they suddenly develop asthmatic symptoms, the problem may not be their health. It could be that there is a buildup of harmful bacteria and dust inside of the air conditioner. Upon realizing the problem is there, you will want to have your ducts cleaned thoroughly and tested for mold.
If you are willing to do it, you can clean out most of the duct work on your own, unless there is mold present. It requires a vacuum cleaner with a hose and paper towels, a brush, and a little bit of time. The only thing that you may want to get help with is cleaning the fan that is in your heat and air unit, because you do need to shut off power before opening the cover on it.
If you decide to get a professional to come clean out the unit and all ducts for you, you should expect it to cost at least $300, depending on the size of your home. A larger home will have more ducts to clean. The trick is, you have to watch out for companies that claim they will clean your ducts for less, because often it is a scheme and they will try to charge you more than it is worth in the end.