Whenever I ask people about firestop, many don’t have a lot of answers. It just leads to more questions.

I discovered this troublesome feedback loop a couple of years ago when I was talking with a building inspector in Chicago.

Now, I realize that you shouldn’t always listen to what building inspectors tell you, because depending on the inspector, his mood, the time of day and the day of the week, you might get a different answer each time.

But I listened up when he told me that a certain building—which the owner has asked me to keep anonymous—needed firestop in its basement. The old building had just received major plumbing and electrical work, leaving its walls full of holes.

The inspector recommended “shooting some foam in there.” And make sure it has a fire rating, he added. No problem, I said. Thanks for the safety tip. After discussions with the building owner, I was asked to help pick out said foam, which began my feedback loop.

I promptly figured out that virtually nothing at the big box stores would do the trick. Forget “Great Stuff.” It’s not rated for fire—at least it wasn’t at the time. The company now has a fire foam, I’m told. Thanks a lot, guys. You’re a day late and a dollar short.

I broadened my search to Google, and that’s when I discovered Boss 813 Expanding Firestop Foam. That sounded pretty impressive. I downloaded the technical data sheet, which includes a funny photo of the can seemingly engulfed in flames.

It also contained the phrase, “Conforms to ALL building codes.” O.K. That sounded good enough to me.

I called the company, asked where I could buy some foam and was directed to its local “distributor,” which turned out to be an apartment condo association on the South Side of Chicago. I got the maintenance guy on the phone.

“Sure, come on down here, and I’ll give you some of this stuff,” he said. His building was undergoing a major renovation, too, and needed to close up a lot of a holes. So many holes, in fact, that he had become the largest wholesale consumer of Boss 813 Expanding Firestop Foam in all of Chicagoland.

After a 20-minute training session on how to apply the foam, which is very sticky at first, hardens in about an hour and sort of resembles a red Icee drink in color, I took delivery of a case of foam and handed it off to the building owner on the North Side.

Just to be safe, I thought it would be a good idea to put in a call to Bill McHugh, the executive director of the Firestop Contractors International Association, based in nearby Wheaton, Ill.

That turned out to be a bad idea, because McHugh lectured me on why my selection process was completely flawed. “It’s a technical sport,” he said. “It’s not just throwing a bunch of goop in a hole. It’s fire science, not goop science. That’s where people get confused.”

McHugh then walked me through the Underwriters Laboratories website, which is full of little nooks and crannies explaining which ratings apply to which substrates. It’s a real maze.

After all that research, I’m still not sure if Boss 813 Expanding Firestop Foam was the right foam for the building. Heck, I’m not sure if it was the right foam for the official Chicago distributor’s building, either. How can manufacturers get away with such confusing-sounding claims as "conforms to ALL building codes?" Isn't that a tad misleading?

In firestopping, confusion reigns. “I’m very embarrassed by my industry,” McHugh admitted. Either way, the job is done. The holes are filled in. And the building inspectors are satisfied.