Commercial exhaust systems serve to vent odors, moisture, and smoke from indoor spaces such as locker rooms, commercial kitchens, and bathrooms to the outdoors by way of a fan—similar to the way a home's kitchen or bathroom exhaust functions but on a much larger scale. These systems are continuously pulling bad air (dirtied with foul odors, moisture, smoke, cooking smells and oils, etc) from a large and crowded space. For this reason they tend to become quite dirty with filth and grime. When this product of exhaust builds up too much inside the ducts, proper venting to the outside is restricted, resulting in odors and moisture lingering in the occupied space. This has the effect of making the room in question "stuffy" and malodorous, and generally exhibiting poor air quality and circulation.

​The above set of before and after images was taken inside a stretch of flexible ductwork belonging to the exhaust system of a municipal community center's locker room. The building itself was constructed in 1998, and the exhaust system had never been cleaned. The resulting accumulation of filth and fluff is visibly evident.
 
Because the area of the room being exhausted (in this case a locker room) is heavy with moisture and warmth from frequently running water, hot showers, hand and hair dryers, etc, the debris exhausted tends to stick quite readily to other particles and to the venting itself, causing a cumulative, clumpy buildup that's as stubborn as it is unsightly. 
 
The flex duct above was cleaned using the Viper Clean Sweep System, a multi-tentacled whip attached to an air hose. When engaged, the plastic tentacles thrash vigorously to and fro, loosening debris from every crevice for the vacuum to swallow up. 
 

Once the length of flexible duct leading from the locker room had been air whipped, it was time to tackle a larger run of rectangular metal ductwork that followed from it. Because this duct was large enough to accommodate a person, the crawl-through method was used to clean it. During this process, the technician dons personal protective equipment (PPE) and crawls through the duct on his hands and knees, armed with an industrial vacuum with brush attachments, physically brushing the debris from the walls of the ducts and into the vacuum.
 
In this case, the technician moved through the length of the duct until reaching a large turbine fan, which was also caked with locker-room grime.

Having thoroughly cleaned the fan, the technician then turns his attention to the 15-foot section of rectangular duct remaining before the outside grille. This section is also cleaned with the crawl-through method, with the debris manually brushed off the walls of the ducts going straight into the industrial vacuum, which sits below. (The technician enters the duct with enough hose to accommodate the length of the duct.)
 
The final step is to clean the outside grille that sits like a window on the exterior of the building. The same manner of dust and grime found inside the flex duct and rectangular duct clogs the tiny holes on the screen of the exterior grille. To clean this, from the inside, the tech washes it thoroughly with a pressure-washer. While most of the excess water from this process runs down the side of the building, whatever is left inside the duct is sucked up with a wet-vac.
 
The ultimate result of this days-long job is a community center whose occupied spaces boast a visibly cleaner venting system, improved indoor air quality, fewer odors, and a generally improved atmosphere. 
 
Wanna learn more about the process of commercial air duct cleaning, the various components cleaned, and the tools employed? 
 
View Commercial Duct Cleaning Page
 
Many thanks to our commercial project manager Ben S for contributing photos and wisdom for this article.

The heat exchanger pictured is definitely not representative of our typical job. Furnace cleaning, when performed regularly, is relatively uneventful, as the technicians use high-pressured air triggers to clean various components inside the furnace, and check key areas for proper function. The goal is to rid the furnace and its inner workings of dust and debris that hinder efficiency and that increase the number of contaminants polluting indoor air. As in any frequent task, however, sometimes unusual or exemplary situations present themselves

The symptoms

This month a homeowner in St Paul contacted us and scheduled a furnace flue cleaning as well as a furnace cleaning. His gas furnace, manufactured in the 1950s, was less efficient than it had been (not surprisingly, some would say). More importantly, he felt it was not drafting properly. He was getting what he called "funny smells" in the house, and the carbon monoxide detectors were going off. The customer attributed this to a clogged furnace flue, which is certainly not an unlikely cause. The furnace flue serves to vent harmful gases produced during combustion to the outside, so if it is clogged or otherwise hindered, it stands to reason that a primary indicator would be the CO detector registering concerning levels of carbon monoxide.

The diagnosis

After listening to the homeowner's concerns about the furnace not drafting properly, the technician proceeded to clean the flue, expecting to find it clogged, perhaps with animal nesting or other debris. Though quite dirty, however, it was not so dirty that one would have expected air flow to be greatly hindered or draft compromised.

The problem became apparent, however, when the technician was able to see, by way of the access created for the flue cleaning, down into the heat exchanger. It was completely clogged and black with soot, to an extent he'd never seen before. It was clear to the technician that a through cleaning was urgently needed to unclog it and restore it to working order, if possible. 

A disclaimer would be in order at this point. The average lifespan of a furnace is about 20 years, and the furnace in question was significantly older than that. The customer insisted, however, that it was otherwise working properly and he simply did not have the funds to replace it. Wanting to accommodate the customer's financial situation, the technician agreed to proceed with the disassembly and cleaning of the heat exchanger, with a thorough explanation of what he was doing and the risk involved, and an assurance from the customer that if the symptoms persisted after the cleaning he would consult a repair company.
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An interesting aside: furnaces of this age rely on natural draft to exhaust gases and are not equipped with a draft inducer. This component is essentially a fan, found in modern furnaces, whose purpose is to create draft and move the products of combustion from the furnace up and out the flue. A furnace equipped with a draft inducer likely would shut down rather than becoming as clogged as this one had, in accordance with its sequence of operation.

The solution

The technician began the job by removing 17 nuts and bolts from the panel just to gain access to the heat exchanger. As soon as the panel was removed, it was clear that the gasket surrounding it was completely deteriorated and needed to be replaced. The customer purchased a new one while the technician performed the cleaning.  

It is unusual that a technician would need to go to such lengths to access a heat exchanger. Typically the heat exchanger is readily accessible, or requires only minimal disassembly in order to access it for cleaning. Moreover, many technicians would likely have passed on this job once observing the amount of buildup needing to be cleaned and the relatively laborious process of accessing the heat exchanger. Likely the customer would have been counseled to simply replace the furnace. However, a combination of a genuine wish to help a homeowner in a tough financial situation and the desire to successfully tackle a challenging and uncommon task inspired our technician to complete the cleaning.

Once the heat exchanger was accessible, the cleaning was carried out using a powerful industrial vacuum and various attachments, specifically a 3-inch round brush head. Because the heat exchanger and its associated tubes were so large, it was easy to fit the vacuum and its attachments down each tube, which made this aspect of the cleaning relatively easy, taking only about 20 minutes.  

On completion, the customer replaced the gasket with the one he had purchased, and the heat exchanger panel was reinstalled. 

The lesson

The heat exchanger after the cleaning was not necessarily a thing of beauty, but it certainly was in a much improved condition to carry out its function of heat transfer. In the end, the tech was wiser, the customer was well-informed and happy, and he also was not out thousands of dollars for the purchase of a new furnace—at least not today.
Wanna dig deeper? Download our free tipsheet: 5 Questions to Ask Before Hiring a Furnace Cleaning Company. 

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Many thanks to our technicians Ben S and Roy S for lending their expertise to this article.