When Is Duct Cleaning Appropriate?

In recent years, ventilation duct cleaning has grown into a huge industry, in response to increasing public concern about indoor air pollution. The industry claims that cleaning ductwork can improve indoor air quality, control molds and other allergens, enhance heating, ventilating, and air-conditioning (HVAC) system performance, and reduce energy costs. Yet there is little scientific evidence to support these claims and poor duct cleaning practices can actually cause or increase air quality complaints.

Latest Findings

Despite more than two decades of research, there is still not enough evidence to draw solid conclusions about duct cleaning benefits on indoor air quality, occupants’ health, HVAC system performance or energy savings (according to a 2010 review of scientific studies on duct cleaning). The review did find clear evidence that ductwork can be contaminated with dust and can act as a reservoir for microbial growth under normal operating conditions. Yet, even when duct cleaning was extremely efficient at removing contaminants within ducts, the effectiveness of reducing indoor air pollutants was highly variable, and in many cases, post-cleaning levels of contaminants were higher than pre-cleaning levels.

When is duct cleaning appropriate?Heat register/vent

Although the value of regular duct cleaning remains questionable, the U.S. Environmental Protection Agency (EPA) and indoor air specialists agree that duct cleaning (or, in some cases, duct replacement) is appropriate in the following circumstances:

  • Permanent or persistent water damage in ducts.
  • Slime or microbial growth observed in ducts.
  • Debris build-up in ducts that restricts airflow.
  • Dust discharge from supply diffusers.
  • Offensive odors originating in ductwork of HVAC component.

In all cases, duct cleaning should be undertaken only after the source of the contaminant has been identified and controlled; otherwise, the problem will not go away. For instance, the water source causing mold growth must be identified and controlled or duct cleaning will be only a temporary fix.

Prevention of duct contamination is key to avoiding problems: Follow these recommendations to avoid the need for costly duct cleaning:

  • Perform routine preventative maintenance of HVAC systems by complying with manufacturer schedules for changing HVAC filters and cleaning coils and other components.
  • During building renovation, seal ductwork to prevent construction dust and debris from entering the HVAC system.
  • New ductwork often contains oil and debris. Before new ductwork is connected to the air handling system, it should be inspected for cleanliness and cleaned if necessary.
  • Maintain good housekeeping in occupied spaces.
  • Ensure that air intakes are located away from contaminant sources.
  • Consider routine inspections of ductwork. TheNational Air Duct Cleaning Association’s (NADCA) standard “Assessment, Cleaning and Restoration of HVAC Systems”recommends that HVAC systems be visually inspected for cleanliness at regular intervals.

If duct cleaning is determined to be the best option:

Hire a duct cleaning contractor who is a member in good standing of the NADCA.Duct cleaning companies must meet strict requirements to become NADCA members. Among those requirements, all NADCA members must have certified Air Systems Cleaning Specialist (ASCS) on staff that have taken and passed the NADCA Certification Examination.


  • Duct cleaning should only be undertaken as a last resort, after other measures have been exhausted.
  • Duct cleaning should only be done after the problem has been thoroughly evaluated and the source has been identified and controlled.
  • Prevent dirt, water and other contaminants from entering the ducts in the first place by following good practices for preventive maintenance and housekeeping, as well as proper location of air intakes.

3 Responses to “When Is Duct Cleaning Appropriate?”

  1. I think you are probably right about duct cleaning. Also the right time of duct cleaning is when you feel your duct needs to be clean you should give it a service.

  2. Its excellent blog and very useful info thanks for this info… heating and cooling mississauga

  3. Duct cleaning it is probably one of the most important elements of maintaining your home in a healthy and fit condition doing on it and a regular bases it well ensure the safely of your family as well.

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