The ductwork Karo Sheet Metal needed to install at the New York School of Interior Design’s new 20,000-square-foot graduate center was different, especially for a nonmedical facility.

It couldn’t just be ordinary duct. According to the specifications handed down by general contractor Whiting-Turner, it had to be germ-fighting anti-microbial ductwork - 25,000 pounds of it.

Usually that meant buying expensive steel coils with a coating already applied, but Joe Portman, Karo general manager, was looking for something more economical, yet still effective.

Through an Internet search, he found Bio Shield Technologies, a Pennsylvania-based company that offered anti-microbial coatings which could be applied to regular steel in the sheet metal shop. Such an approach saved money, since Karo workers could brush on or spray the fungus-fighting material themselves instead of ordering it already on the steel coils.

Portman decided to try its product, Silver Bullet AM. The acrylic resin-based product contains mold-fighting agents from Agion. The makers of Silver Bullet AM say it offers long-term control of germs and bacteria.

Learning as you go

It was the first time Karo had used anything like it.

“It was a learning curve,” he said. “We had to figure out how to mix it, how much water to use.”

But that didn’t take long, just a bit of fairly simple mathematics.

“Each day we had to do calculations on how much duct we had to paint, and then at the end of the day we would mix it up and then spray it or roll it on, and let it dry,” Portman said.

Karo just bid on another project where it hopes to use Silver Bullet.

“We would definitely use Bio Shield again,” Portman said. “It worked out pretty good.”

Jeff Drucker, spokesman for Bio Shield, said the company has been marketing it to HVAC contractors for at least three years, but interest has been building lately, especially as contractors look to contain costs.

Buying steel can sometimes lead to sticker shock, Drucker added.

“The first call they usually make of course is to their steel supplier,” he said. “And the first thing they also find out is the tremendous expense associated with the (pre-coated) steel. Also the usual minimum quantities that they have to buy, and then oftentimes they have to have so many gauges, so many widths.”

Less cost

It can get expensive, not to mention the lead times required, Drucker said. Using the shop-applied anti-microbial opens up a chance for contractors to bid on jobs no matter their size.

“I think we really provide a tremendous service to the fabricators, the mechanicals and the guys who are doing this duct,” he said. “Yes, they have to learn a little bit of something new. Sheet metal workers have to become ‘painters’ to a certain degree - but not expert painters.”

Bio Shield provides training to contractors on how to use the product.

And the product has been used all over the country, on projects ranging from airports to commercial buildings, colleges and even TV studios.

One example of a school that now contains duct with the shop-applied anti-microbial is Bucknell University, a private liberal arts college in Lewisburg, Pa. Precision Sheet Metal LLC of Scott Township, Pa., was hired to make the spiral and rectangular ductwork for the school’s project. It sprayed the ductwork with Silver Bullet to meet the project’s specifications before turning it over to the installing contractor.

“It worked very well,” said Rob Evans, Precision’s owner. “We were very happy with the product.”

Another benefit: After drying, it has an attractive, high-gloss shine.

“It’s almost like a finish on a car,” Evans said.

Since making the duct for the university project, Precision officials have since used the anti-microbial as part of its work on a blood plasma donation center. And they have invested in custom-made sprayers to apply the coating, and plan to use it frequently.

Drucker said he hears such comments frequently.

“There are so many things that they love about this, once they embrace it,” Drucker said. “And more and more people are embracing it.”

For reprints of this article, contact Jill DeVries at (248) 244-1726 or email