The services to watch out for are called blow-and-go in the trade. Contractors who provide them might not be licensed, probably are not members of any trade association and often spend less than an hour in your house. And often have high pressure sales tactics that can lead to bills many times the amount of the offered special.
Sales pitches for blow-and-go work often include sweeping but unsubstantiated claims about the health benefits of duct cleaning, claims of EPA certification or approval (both bogus) and recommendations for annual duct cleaning, which is unnecessary, as part of your annual appliance service.
Worse yet, contractors using inadequate vacuum collection systems and short-cut cleaning procedures can cause more problems than they solve. According to the EPA, these substandard jobs can release more dust, dirt and other contaminants into the air than simply leaving the ducts alone. Cost and time estimates vary because of the different sizes of houses and complexities of duct systems. But the EPA says that a professional cleaning should cost from $450 to $1,000 and take four to eight hours in a typical three- or four-bedroom house.
Proper procedure, according to NADCA, is to place the system under negative pressure with a powerful vacuum and insert various brushes and cleaning apparatuses into the ducts to dislodge debris, which flows to the vacuum. NADCA guidelines allow both vacuum equipment that exhausts particles outside of the house, and inside-exhaust systems fitted with HEPA filters.
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