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To people outside of the HVAC industry (Heating, Ventilation, and Air Conditioning), the various elements that make up the HVAC system can seem murky and vague and consequently are often conflated. The term "furnace ducts" is an example of this tendency. Furnace cleaning and air duct cleaning are sometimes confused, and we often have customers request one when what they really want is the other (or both). Here's the run-down.​

What is Furnace Cleaning?

Furnace cleaning involves only the individual components of the furnace itself—like the heat exchanger, the blower motor, the combustion chamber, burners, fan, etc. These are typically cleaned with the combination of high-pressured air and an industrial vacuum. Some of the heavy-lifting furnace parts, like the evaporator coil, often require a more specialized cleaning for an additional cost.

A quality cleaning minimizes debris in the unit and improves air flow, increasing energy efficiency. It will also reduce the number of contaminants and particles entering your air ducts only to recirculate throughout the system. Furnace cleaning typically does not include cleaning of the ductwork and vents associated with the furnace.

What is Air Duct Cleaning?

Air duct cleaning is the process of removing dust, debris, and contaminants from your air ducts, including the main supply trunk and main return, as well as the branch lines. Laypeople sometimes refer to it as "vent cleaning," though this term is a little reductive: air ducts are the vast system of (usually) metal tubes that run from your furnace throughout your home, distributing heated or cooled air; vents are simply the point where the ducts open into the house. 

Duct cleaning utilizes specialized tools such as air whips, snakes, and wands to move debris through the ducts toward an industrial vacuum for removal. Typically, different tiers of service are available, depending on how dirty the ducts are and how long it's been since they were last cleaned. 

How are the two services similar?

Air duct cleaning and furnace cleaning use similar tools: high-pressured air, powerful suction, and sometimes agitators. They both contribute to energy efficiency and improved air flow (and air quality) by reducing the amount of debris and contaminants hindering the HVAC system. The two services are often performed in tandem, for the most comprehensive system cleaning. Because the air ducts and furnace form part of the same system, it is highly likely that if one is dirty, the other is too.

Which service do I need?

For reasons stated above, it is usually a good idea to have both the furnace and ducts cleaned at the same time—but this is not a hard and fast rule. If your furnace is new (a year or so), and has a properly fitted filter (this is key), it may not need a cleaning yet. However, if your furnace is dirty, it is virtually guaranteed that your air ducts are as well, since the furnace blows air directly into the supply ducts.

Regarding air duct cleaning, it is generally recommended that this be performed every two years. Ideally you would start with the highest level of service and then the "maintenance" level service will suffice for the next few cleanings. If you are unsure whether you need either service performed, you can request that the technician conduct a visual assessment and discuss with you (and show you) his findings. 

To simplify things and maintain a schedule that's easy to keep track of, it's advisable, when first taking up residence in a new home, to have both the air ducts and the furnace cleaned at the highest level so you can be sure that indoor contaminants and debris are minimized. For services thereafter, if you keep on a regular schedule, you'll pay less for the cleaning, and many companies offer a discount on multiple services, increasing the benefit of having both services performed at once.

Wanna dig deeper? Download our free tipsheet: 5 Questions to Ask Before Hiring a Furnace Cleaning Company.