If you have had your ducts inspected and mold growth has been detected on hard surfaces you should have mold removed and it would be a good idea to have ducts cleaned. Other microbials can look like mold, so it is best to have it professionally tested to confirm mold. Find the reason for the mold and correct the problem before cleaning ducts.
Also, if your ducts are extremely dirty and you have severe allergies, it would be a good idea to get your ducts cleaned. In this case too, you would want to take a look at your filtration system to find out why dust is getting into your ducts.
The air within your home has pollutants that can affect your health. Some of the pollutants will come from outside, but some will come from things like, cleaning, cooking, building materials, furniture or other consumer products. Volatile Organic Compounds (VOC’s) are a contaminant commonly found indoors as a gas. Particulate matter such as formaldehyde, pollen and mold can also be found indoors.
The best way to help with this is to ventilate with outside air. This will help to reduce or remove these pollutants from your indoor air. Air purifiers also known as air sanitizers that are portable can help a room or an area. Installing specialized filtration integrated with your HVAC system will help filter your whole house.
A whole house fan will definitely help to freshen up the air in your home and reduce or remove pollutants. Even here in Southern California, the air inside your home has more pollutants than outside. Not only can it help ventilate your home, it will help to cool your home on those cool mornings days, or evenings. Quiet Cool is one brand that works well and is quiet like its name says. There are other brands as well, like Ventcool. This is meant to be a guide. We are not absolutely saying you must have a whole house fan.
The EPA has a great website and is full of all kinds of information.