Case Study: Medical Clinic Dryer Vent Cleaning

For this project, we got a call from a contractor working with a medical clinic in Washington County, Minnesota. One of their dryers had experienced a disconnect in the dryer vent line, causing lots of moisture and mold that the contractor was working on remediating. They hired us to clean the dryer vent.

The dryer vent line was 4 inches in diameter and over 100 feet long. From the dryer, the vent line extended up into the ceiling, zig-zagged across the hall through two rooms and then to the outside of the building.

The diagnosis: bird’s nesting clogged the dryer vent

On arrival, our commercial technician began the process of cleaning the vent. Our standard process is to insert a reverse-blowing spinning air ball from the outside vent, push it toward the back of the dryer, and then pull the tool out, bringing any lint with it. In this case, however, the tech could feel and hear that there was a disconnect in the vent line. The dead giveaway of a disconnect is the tool going silent, as it does when it escapes the vent line and enters a wall. From experience the tech was able to discern that the disconnect was right behind the outside wall. He entered the clinic, removed a ceiling tile, and immediately observed a bird’s nest in the vent line, just after a disconnect.

Medical clinic dryer vent cleaning
A birds’ nest clog, which blocked the escape of moisture and lint from the dryer, was responsible for the disconnect in the dryer vent line.

Birds’ nesting can fully block a dryer vent line. When this happens, the moisture from the dryer cannot vent properly and water will quickly pool at the site of the clog. If the water escapes through a seam in the vent line, it will soak and weigh down any exterior insulation that wraps the duct. In this case, the weight of the bird’s nest, the pooling water, and the soaked insulation seems to have created the disconnect in the vent line.

The solution: disassembly and creating access

To clear the bird’s nest clog, no tools were necessary—the tech simply reached in and pulled it out in clumps by hand. The rest of the vent line, however, was another matter. Since the vent line was over 100 feet long and the maximum length of the air line is generally 40 feet, access was needed not only from the outside but also at one or more points inside.

To achieve this, the technician created a 1-inch access hole at a point just before where his tool could not reach from the outside. From this access he inserted the tool to clean toward the booster fan that was positioned in the vent line about 12 feet from the dryer itself, then again from the other side, from the dryer to the booster fan.

Unfortunately, due to all the lint buildup as a result of the bird’s nesting, the booster fan too was fully clogged. To resolve the clog in the booster fan, the technician took to it an industrial vacuum with a small attachment, successfully removing all lint.

A booster fan in a medical clinic dryer vent line that's clogged with lint.
A booster fan in the dryer vent line, positioned about 12 feet from the dryer itself, was clogged with lint.

The lesson: install bird guards

Because of the amount of moisture in the dryer vent line, a perfect cleaning was not possible. The vast majority of lint was removed, and a flow test demonstrated good air flow. However, since wet lint is sticky, a small amount remained. The technician recommended the client use the dryer as normal for two weeks, during which time the remaining lint could dry. After that time we’ll return to clean the remainder of the lint from the vent line.

A dryer vent bird cage placed over the exhaust of a medical clinic dryer vent to prevent animal entry.
A bird guard dryer vent cover, designed to keep birds and other animals out but allow for the venting of hot, moist air and lint.

The final step of this day’s project was to install a bird guard at the dryer vent termination. These are specially designed to cover the dryer vent exhaust and prevent birds and other animals from entering, but crucially, to still allow for the exit of hot air, moisture, and lint.

The lesson, in commercial dryer vent cleaning as in life, is that an ounce of prevention goes a long way.

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