Oh my goodness! My family have been so ill this winter and I suspect that the ducts have something to do with it. I'm going to have my basement checked for radon as well. Thank you so much for your comments. I will pass them along to whomever will listen. Stay well!
The other thing that struck me was that every person who had their ducts cleaned as a result of our experience found lots of bad stuff and felt better after the job was done. One of my friends only found mouse droppings and dried urine. For the most part, her ducts weren't bad. But her son's (mild) allergies cleared right up.
After it was over, I wanted to do public service announcements! lol! I's just my opinion, but if I was asked to hazard a guess, I'd say that dirty ducts are probably a big problem for more than 50% of the population.