When HVAC systems need cleaning

The cleaning process

Duct cleaning is usually done during off hours, when operations are shut down, so cleaning contractors work nights and weekends. Duct-cleaning equipment varies by company and even by region, but there are two basic technologies: contact cleaning and negative-air cleaning. With either method, each part of the HVAC system gets cleaned, including the registers, coils, air hander and ductwork.

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Contact cleaning is the old-school method. The ductwork is hand-vacuumed. If the ducts are large enough, a technician crawls the interior. If not, the ducts are cleaned by cutting access holes every 15 feet or so, reaching in and vacuuming. Contact cleaning is the most thorough method but, because it can be more labor intensive (and thus more costly), it’s not used very often. However, even on some modern jobs, part of the work might require contact cleaning.

Negative-air-cleaning technology has been developed during the last 20 years. It involves a large vacuum (known as a negative-air machine) attached to a duct opening to produce a powerful draw of air through a section of ductwork. A variety of tools can be run through the duct while the vacuum is operating. Hoses can blast air and augers (long cables with a spinning brush on the end) can agitate the particulate into the air stream for the negative-air machine to collect.

Regardless of approach, industry best practices say that it’s insufficient simply to connect a strong vacuum up to the duct. Some kind of contact agitation, such as air blasting or mechanical brushing, is required on the interior duct surfaces to remove particulates more effectively.

Design problems

Manufacturing processes can release oil mist, lint, sawdust and all manner of particulate matter into the air. Any HVAC system is at risk for contamination in such an environment, particularly if the return or intake registers draw air from the particulate-filled zone. Such contamination not only increases energy costs, but can be a fire hazard if the material is flammable.

Some industrial and commercial venues can exhibit serious HVAC contamination. This is particularly true if a system shares air with industrial processes that release airborne particulate matter. Lint can also clog the filters and coils and cause rapid ductwork buildup.

A quality HVAC system can be a luxury when it runs well with little attention. But, just like dependable old friends, they occasionally let us know they need a helping hand. When they become overloaded with particulate and debris, problems begin. HVAC cleaning is a well-established procedure for remedying a contaminated system. When done properly by a reputable company, it can improve air quality, restore system functionality and reduce the cost of running it.