When you have real dirty air duct in your central heating plus air conditioner system unit you have to get what is called a deep air duct cleaning, getting a deep air duct cleaning is a bit uncommon than getting a respected air duct cleaning, and when you get a deep air duct cleaning you need to pay more than you would for the respected kind, however this is because the deep air duct cleaning is a much more complicated process plus will take your heating plus air conditioner specialist from the local heating plus cooling supplier much longer plus much harder work to accomplish. I had to do a deep air duct cleaning recently because it had been so long since I last had the air duct of my central heating plus air conditioner system unit cleaned. This was totally my fault for being forgetful. If I had remembered to have the air duct of my central heating plus air conditioner system unit cleaned respectfully I would not have had to hire the heat plus cooling system supplier’s most certified plus superb heating plus air conditioner specialist to do the deep air duct scrub on my central heating plus cooling system unit! This was a wonderful lesson learned to me plus from now on I will get my air duct cleaned on a respected basis so I never have to pay the extra cost for a deep air duct cleaning again from the local heating plus air conditioner supplier! This is an extra expense I did not by any means want or need to spend.