Hospitals’ Ailing Ductwork Finds Cure in Aerosol-Based Sealant

Oct. 18, 2018
Looking to improve indoor air quality while minimizing operational disruptions, two California healthcare facilities used a "non-invasive" aerosealing procedure that allowed them to find and plug leaks from inside their duct systems.

By NEAL WALSH, Aeroseal LLC, Dayton OH
Ranked as one of the nation's top hospitals, John Muir Medical Center in Walnut Creek CA is a showcase for excellence in everything it does – from medical care to building, design and construction. In 2016, when the hospital decided to turn existing space on its second floor into a new Endoscopy Surgery Unit, it also had to repurpose the existing mechanical system serving the space.

Pretesting, however, had indicated inadequate airflow, resulting in unacceptably low levels of exhaust throughout the unit. Further investigation indicated that the limited airflow was due to duct leakage. That prompted mechanical contractors on the project to suggest using aerosol-based duct sealing to shore up the leaks.

Unlike traditional duct sealing methods, the aerosol technology seals duct leaks from inside the ductwork. The sealant is delivered to the duct interior via a long flexible tube that connects the computerized sealing system to a temporary entryway cut into the ductwork. Prior to sealing, foam plugs are used to temporarily block the registers, ensuring that the only escape route for air being blown through the tubing and into the duct system is via the multitude of leaks. When filled with a constant mist of sealant, the pressurized air drives the particles of sealant to the individual holes where they bond together and form a tight, permanent seal over each leak.
“By blocking the registers and using the system’s fan to pressurize the ductwork, the computerized equipment allows us to measure the leakage rate before sealing begins,” said Mark Avila, president of Air Seal Solutions, San Jose. “It then monitors the leakage rate during the sealing process itself and lets us know when we have reached the level of tightness we’ve targeted. At the end of the process, we are able to print out an official report that shows the before and after results of the work we’ve done.”Not only does the aerosol sealing process allow technicians to monitor the results as they happen and eliminate the need for retesting, its automated technology ensures that all the leaks are found and sealed. Testing conducted in 2001 by the U.S. Department of Energy found that the aerosol duct sealing method was 50% more effective at sealing ductwork than using tape or mastic. For hospital administrators at John Muir Medical Center, it was the promise of effective results with minimal disruption to normal facility operations that was key to their decision to proceed. By working from the inside of the ductwork, the aerosealing procedure allowed easy access to the entire duct system without the demolition and wall reconstruction typically associated with duct renovation. It was also important that the sealant itself does not coat the duct interior, but instead remains suspended in air as it is drawn to the multitude of tiny leaks throughout the duct system.
During initial meetings with hospital administrators, Avila explained how the technology worked and alleviated any concerns that may have existed regarding the safety of the materials being used and the impact on hospital operations. With his company’s expertise in clean-room mitigation, Avila was also able to demonstrate how his team would actively monitor the air quality of the space during the sealing process and protect the highly sensitive equipment present in many of the rooms from being potentially affected.Along with leakage issues, initial duct inspection found that there were other structural issues effecting the integrity of the duct system. “We first taped the leaks around the easily accessible ductwork and shortened other areas where design issues were a concern,” said Peter Spadia, the hospital's project manager. "We then aerosealed the majority of ductwork where leaks were difficult to reach.”It took Air Seal Solutions just a single weekend to aeroseal the two designated sections of highly inaccessible ductwork. In the end, 1,583.4 CFM of leakage in these sections was cut to just 222.1 CFM – an 86% reduction. During the entire process, testing showed airborne particles of sealant remained well below ISO 9001 levels.A final report generated by the aerosealing system showed that the sealant had eliminated enough leakage to meet industry regulations and allow sufficient ventilation to easily pass the hospital’s strict building code requirements.“The technology worked,” said Spadia. “If you have an existing mechanical system that is 10 to 20 years old, you can make it like new again – give it new life. We are planning to convert a number of buildings into doctor suites and I can see aeroseal technology being a viable solution here as well. For new construction, it can be used to seal the entire duct system once it’s been installed.”

New Construction

At Sutter Solano Medical Center in Vallejo, it was all about regulatory compliance. The engineering team at the Northern California hospital had been working for weeks on a new ventilation system that had been installed to exhaust air from the center’s new autoclave sterilization room. No matter how many times they went at it, however, they could not get the ducts sealed tight enough to draw sufficient air through the system – or to pass OSHPD building code. And now, with walls hiding the ductwork and limited space between the newly installed duct and the ceiling, several subsequent efforts at manual re-sealing proved increasingly futile. Worst of all, final inspection was scheduled for the following Monday, so the contractor had to have the system up and running properly by the end of the weekend.

Instead of having to tear down the newly constructed walls to access and seal the leaky ducts by hand, Avila and his crew used the aeroseal technology to access and seal the leaks from inside the duct system. Not only did this approach alleviate the added time and expenses related to deconstruction, but it guaranteed that contractors would meet code followings its application.

“We were able to monitor the effects of the sealing process while we were working,” said Avila. “We knew we had effectively sealed the leaks before we had even finished.”Air Seal Solutions received the initial call on Friday, came in and sealed the work over the weekend, and presented its report to prove results and pass inspection by the contractor’s Monday deadline.Not only did the aerosol duct sealing process allow Sutter Solano to meet its building code requirements, but by reducing leakage to less than 1%, the engineers estimate that the process is now saving the medical center nearly $1,500 annually in reduced energy costs. “Over the years we’ve been called in to solve HVAC performance issues for a number of healthcare facilities,” said Avila. “I don’t believe I’ve come across a single medical facility in my region that couldn’t benefit from having their ductwork effectively sealed.”


Based in Dayton, the author is Aeroseal's SVP for commercial applications. A frequent speaker at industry events, his focus is on building performance and technical innovations that improve HVAC duct system efficiency.