Inside your HVAC system, fine dust collects on the surfaces of air ducts, vents, motors, and coils. Skin, hair and dander flakes from dead pets accumulate in the dust, and before long, this process creates a dense, carpet-like environment where bacteria, mold, dust mites and allergens can thrive. It's easy to forget about air ducts because they are inside walls and out of sight, often overlooked. However, cleaning the air ducts is critical to keeping an HVAC system running.
Dirty air ducts can make your heating and cooling system less efficient and if left uncleaned for too long, they could wear out the air conditioning system and break it. The air that enters the room from the supply vent enters at such a high speed that it creates turbulence in the air. The formation of dirt stains around air conditioning vents usually occurs when the turbulent air from the air conditioner interacts with the dust, dirt, or dander of pets in the room. This interaction causes dirt to adhere to the walls through which the air conditioner is driven. Knowledge about cleaning air ducts is still in its early stages, so a general recommendation cannot be given as to whether air ducts in the house should be cleaned.
The Environmental Protection Agency (EPA) urges you to read this document in its entirety as it provides important information on the subject. Duct cleaning has never been proven to actually prevent health problems nor do studies conclusively show that particles (e.g., this is because much of the dirt in air ducts adheres to duct surfaces and does not necessarily enter the living space). It's important to keep in mind that dirty air ducts are just one of many possible sources of particulate matter in homes. Contaminants that enter the home from both outdoor and indoor activities such as cooking, cleaning, smoking or simply moving around can cause greater exposure to contaminants than dirty air ducts. In addition, there is no evidence that a small amount of household dust or other particles in air ducts poses a health risk.
If any of these conditions exist, it usually suggests one or more underlying causes. Before cleaning, modernizing or replacing ducts, the cause or causes must be corrected or else the problem is likely to recur. Some research suggests that cleaning the components of the heating and cooling system (e.g., however, there is little evidence that cleaning only the ducts) improves system efficiency. You may consider cleaning air ducts simply because it seems logical that they get dirty over time and should be cleaned from time to time. As long as cleaning is done properly, there is no evidence to suggest that such cleaning could be harmful. The EPA does not recommend that air ducts be cleaned routinely but only when necessary.
However, they do recommend that if you have an oven, stove or chimney that burns fuel they be inspected to make sure they are working properly and serviced before each heating season to protect them against carbon monoxide poisoning. If you decide to clean your home's air ducts take the same consumer precautions you would normally take when evaluating the competence and reliability of the service provider. Whether or not you decide to clean your home's air ducts preventing water and dirt from entering the system is the most effective way to prevent contamination (see How to Prevent Duct Contamination).If you decide to clean your heating and cooling system it's important to ensure that the service provider agrees to clean all components of the system and is qualified to do so. In addition, they can propose the application of chemical biocides designed to eliminate microbiological contaminants inside the ducts and in other components of the system. Some service providers may also suggest chemical treatments (sealants or other encapsulants) to encapsulate or cover interior surfaces of air ducts and equipment housings as they believe this will control mold growth or prevent release of dirt particles or fibers through the ducts. These practices have not yet been thoroughly researched and you must be well informed before deciding to allow use of biocidal products or chemical treatments in your home's air ducts. They should only be applied if at all after having properly cleaned the system of any visible dust or dirt.
Knowledge about potential benefits and potential problems of cleaning air ducts is limited since every home's conditions are different it's impossible to generalize about whether cleaning your home's air ducts would be beneficial or not. On the other hand if your family members have unusual or unexplained symptoms or illnesses that you think might be related to your home environment you should discuss situation with your doctor. The EPA has published several publications as a guide to identifying potential indoor air quality problems and ways to prevent or solve them. You may consider cleaning your home's air ducts simply because it seems logical that they get dirty over time and should be cleaned from time to time. While debate over usefulness of regular duct cleaning continues there is no evidence to suggest that such cleaning is harmful as long as it is done properly. On other hand if service provider doesn't follow proper duct cleaning procedures it can cause indoor air problems. For example an inadequate vacuum collection system can release more dust dirt and other contaminants than if it had left ducts alone. A careless or inadequately trained service provider can damage ductwork or heating and cooling system potentially increasing heating and air conditioning costs or requiring difficult and costly repairs later on.
