Low-Ball Offer

• Beware of companies that advertise to clean your air ducts for $99, as of 2008 figures. The NADCA says this should cost between $400 and $1,000, as of 2008.
  
  

Tries to Upsell

• If the representative tries to sell you other, unrelated services to clean your home, such as carpet cleaning or mold eradication, do not bite, warns ConsumerReports.org.
  
  

May Not be Necessary

• It has not been proven that duct cleaning will prevent health problems, according to the EPA. The EPA only recommends having ducts cleaned if there are gross problems such as mold growth, vermin or clogging due to excessive dust and debris.
  
  

Routine Duct Cleaning

• Beware of firms that recommend routine duct cleaning. The EPA recommends that ducts only be cleaned on an as-needed basis.
  
  

Claims of Health Benefits and Certification

• The EPA warns against companies that claim that duct cleaning will produce health benefits. These claims are not proven. In addition, do not believe any firm that says the EPA certifies them. The EPA does not provide certification for duct cleaners.