Commercial duct cleaning technicians have a diversity of tools and methods at their disposal, which they will vary depending on what will be most effective under the given conditions.
Crawl-through duct cleaning
When the ductwork is large enough for a person to fit into, a physical crawl-through will be conducted. Because during the process the technician is in very close proximity to the entire length of the ductwork, this is the most thorough and effective method of commercial duct cleaning available. During a crawl-through, the technician dons protection in the form of a Tyvek suit and a respirator. He enters equipped with a HEPA-filter vacuum with 100 feet of 1 7/8-inch hose and either a 3- or 14-inch dustbrush head. He physically enters the ductwork through a 16-inch access panel, moving methodically through parts of the HVAC system. When he reaches a fire damper or a set of turning vanes, he will create new access on the other side. All access panels will later be thoroughly patched with sheet metal according to NADCA (National Air Duct Cleaners Association) standards.
Tentacled air whips
If the ductwork cannot be cleaned by crawl-through because of its dimensions, a multi-tentacled air whip will be the technician's tool of choice (in the case of Twin Cities Furnace Cleaning, this is the Viper Clean Sweep system). This tool has six 14-inch long tentacles that thrash swiftly and vigorously around inside the ductwork in all directions. This extreme agitation loosens debris, and then a reverse- and forward-skipper ball, alternatively, is used to push debris to the desired location, where the vacuum is situated. This is accomplished by creating a minor access point in the middle of the length of ductwork and sending a back-skipper down one way, then the forward-skipper down the other way, again, toward the vacuum. (The Viper alone will be effective if there is enough suction, but a better practice would utilize the skipper balls in concert with the Viper.)
A rotating brush, or rotary brush, which is essentially a spinning brush-head on the end of a long cable, is a more traditional, less modern tool than the Viper but is still sometimes a better choice for particular conditions. It is often used in transit ductwork, for example, if there's been flooding, or if the transit lines have been compromised by cracks and sand has entered. In this case, the aggressive spinning of the carbide-tipped brush-heads will more effectively dislodge debris. These firmer bristles are also effectively used on uninsulated ductwork, whereas the softer rotary brush bristles are suitable for interior-insulated ductwork. Rotary brush-heads come in 4 sizes (to properly fit the ductwork) in both the hard- and soft-variety bristles.
High-pressured air triggers, etc.
High-pressured air wands or air triggers are a standard tool in any duct cleaning technician's arsenal. Because an agitator (air whip) or contactor (brush) is needed for effective cleaning of ductwork surfaces, air wands are not used alone to clean ducts. Commercially, these are most effective for cleaning components such as reheat coils; after a Viper, or a vacuum with a dustbrush head, has been used to loosen debris, a high-pressured air trigger blows it through the coil to the vacuum. Even something as simple as a foxtail duster is a valuable tool in specific situations, such as cleaning turning vanes and dampers, along with a vacuum.
Of course, the multiplicity of tools and methods available to commercial cleaning technicians is valuable only to the extent that their experience guides them as to which is the proper tool for the given HVAC component/scenario.
Many thanks to our technician Ben S. for lending his expertise to this article.