Most of my long time readers will likely recall that our home flooded last January when our pipes froze. We have spent MONTHS getting things ripped out, cleaned or replaced, and trying to get back to "normal". Well, in July, when it was our record summer of 63 days of temps over 100 (many in the 110 range), our air conditioner decided to go out. Then, in September, we had several things break ALL IN ONE DAY. Things like the Hot Water Heater went out, drains clogged, drains leaking, ice maker going out and leaking water all over the kitchen, dishwasher went out, and on and on. It hasn't been a great year to own this home.
However, in the midst of all of this, there are positives. We are all still alive, and with so many items replaced with brand new, they are at least under warranty now! Other items we had repaired. During the replacement of our hot water heater, we discovered that we have been VERY fortunate that our home hadn't caught on fire. The previous owner had done many repairs himself, without benefit of permits OR proper training, and we had several very dangerous hazards in our home. We don't know why the home inspector didn't catch these things when we bought the house, but nevertheless, the professionals we hired for repair got everything fixed, cleaned up and out, pulled proper permits, and had the city inspector make sure it was all done properly and to code.
So often I am afraid that many people take on home improvement tasks like our previous home owner did, and they are not properly trained, and don't know the proper rules, regulations, safety measures, and codes that need to be followed for safety. Yes, it may save you a few dollars in repair costs, but if you do something improperly and your house burns down, you haven't really saved yourself anything at all. In fact, you've cost yourself quite a bit of money.
My recommendation is that if it involves gas lines, electrical lines, certain types of plumbing, and/or anything else that requires a license to work on: DON'T do it yourself. Spend the extra money for a professional. There are many places such as http://www.thesteamteam.com/austin-restoration-services/smoke-fire.shtml whose company does air duct cleaning work and so much more.