Building engineers find the answer to HVAC problems with Nerva Duct Seal at Mt. Zion Hospital

Renovations to UC San Francisco Hospital Pharmacy comes to a two month standstill while engineers work to solve exhaust leakage issues. 40 minutes of Nerva Duct Seal and the job was solved.


96% leak reduction; vent hood functioning; pharmacy certification


UCSF Medical Center at Mt. Zio


San Francisco, CA


Reduce pharmacy ventilation hoods duct leakage

Before Sealing

580 CFM leakage

After Sealing

23 CFM leakage

The Mt. Zion Hospital Pharmacy’s two new ventilating hoods require sufficient exhaust or else a fail-safe system will register a malfunction and equipment will automatically shut off. This is where chemo chemicals are prepared so it is critical that all air borne particles be exhausted from inside the hoods via connecting ductwork that leads outside the building. Even after meticulous construction that included manual sealing of all 300 feet of twisting ductwork, the exhaust system was simply not providing enough pull to meet code or to keep the system running properly.

Over a two-month period, the best and brightest tried solving the mysterious exhaust malfunction. The ventilation unit was examined for faulty readings. The ductwork, covered in fire insulation, was unwrapped and manually resealed and rewrapped. With the building’s scheduled opening fast approaching, hospital engineers were at a loss for an explanation or a solution. Then someone suggested trying a new duct sealing technology they heard about.

We tried adjusting the fans, resealing the ductwork and various other solutions. The HEPA filters at the bottom of each unit really exacerbated the effects of the leaks and kept us from getting sign-off on the project. In the end, it took twenty minutes to seal the outside ductwork and another twenty minutes to do the rest… It was a real project saver.

– Rick Schaffel, General Contractor, TCB Builders, San Francisco, CA

With no time left for a test run, hospital administrators, with fingers crossed, gave Coast Environmental, a duct and IAQ specialist, the green light to clean and seal the duct system using Nerva Duct Seal. The sealing process itself took just forty minutes to complete – 20 minutes for each of the two sections of ductwork being sealed. Since this was a 24/7 hospital, the entire process was conducted without interruption to the hospital’s regular operations.

We didn’t know if it would work or not. We weren’t even sure that leaks were the issue. All we knew was that the new ventilation hoods weren’t functioning properly and we were running out of time. So we proceeded on the advice of a trusted consultant familiar with the technology…and it worked beautifully. It quickly sealed the leaks and fixed the problem. Knowing what I know now, I’m confident in saying it was the only real solution to our problem short of a complete laboratory redesign.

– Robert Gaderlund, Project Manager, UCSF Medical Center at Mt. Zion

The engineers could actually watch as holes and cracks were getting sealed. A computer-generated chart showed a plunging line on a graph representing the real-time decrease in leakage. After two months of puzzling over the problem and then 40 minutes of Nerva Duct Seal, the engineers had their solution…and the new pharmacy opened on schedule.

It turned out to be a perfect solution to finding and easily sealing all of the holes and leaks throughout the entire duct system. I love how you can actually see the progress and know it’s working.

– Adrian Welsh, Duct Specialist, Coast Environmental, Carlsbad, CA