If firefighting ever gets old for Lt. Mike Webb or Capt. Lenne Stolberg, either of them could easily take up leading tours around downtown Frederick.
“See those standing up above the skyline? There, there and more over there?” Stolberg said last Wednesday from the top floor of the East All Saints Street parking deck, pointing out the many churches rising above downtown to the recruits of firefighter academy Class 21. “Those are the clustered spires where the city gets its name, the city of clustered spires. And that’s why there are no buildings built in Frederick that are over seven stories, because they don’t want it blocking the skyline of that.”
But the groups on that tour would take on an undeniably sinister edge, as most of last week’s stops ended with either Webb, Stolberg or Fire Medic III Bernie Studds explaining just how well each type of construction would hold up if it were engulfed in flames.
“Most of those, probably all, are going to be heavy-timber construction,” Stolberg said, rounding out the lesson with an evaluation of the building type.
Contrary to the logic that a predominantly wood-based build would be more susceptible to fire, older structures that were built on heavy-timber frames are actually far more fire-resistant that some of the lighter buildings that are typically constructed today, Webb explained.
One reason is that the exposed layer of timber can quickly char over when exposed to fire, preventing the wood beneath from catching rapidly.
In contrast, the recruits also learned about the much lighter wood-frame structures that most modern houses are built on. Often consisting of relatively flimsy walls supporting a roof made of lightweight trusses and oriented strand board (OSB) wood panels, wood-frame homes catch fire and burn much more rapidly.
The lessons in building design were among the first the recruits received in their Firefighter II training, which focuses on fire behavior, building construction types, water distribution systems, fire protection systems and ventilation techniques, among other topics.
Part of Class 21’s lesson included a “live burn” of a small dollhouse made primarily of OSB, a type of engineered lumber. Having seen the model used to teach recruits how fire moves through a building in a lesson posted online by a fire company in Birmingham, Alabama, Webb asked Lew Raeder, a retired battalion chief from Prince George’s County, if he could construct the model based on the plans provided by the fire company.
A few days and $16 worth of supplies later, Raeder was ready to present his model, complete with detachable “windows” and hatches over the roof for the instructors to simulate everything from the effect that ventilating a rooftop can have on a fire on the first floor to how interior walls can fail.
“There’s even a stairwell leading up to these ‘rooms’ on the second floor simulating where bedrooms might be,” Webb said. “So we can show the recruits what happens when they go into a house fire and they properly ventilate versus when they improperly ventilate in a Type-5 lightweight-construction house. It’s an inexpensive way for us to show them in real life the skills they’ll be using.”
As predicted, the burn was an immediate success, as the recruits in Class 21 jostled for a better view of their instructors manipulating the various hatches to simulate backdrafts and over-ventilation.
While the initial plan was to try for two uses of the dollhouse, the perils of its lightweight construction ultimately made the model burn up even faster than Webb could put it out, using first a common household spray bottle, followed by a compressed water tank to quell the blaze.
“Yeah, get some!” several recruits cheered as a valiant effort was made to extinguish the flames.
Realizing their efforts were likely in vain, the instructors decided not to waste the opportunity to pass even more knowledge down to their wards.
“Did you all hear it?” Webb asked as a loud “whoosh” accompanied Studds opening the front door of the model.
The recruits cheered again as the blaze kicked up in intensity, feeding on the oxygen just introduced to the lower floor of the model to climb higher into the building.
“See it building right back up?” Studds asked next. “What did it not have before we opened that door?”
“Oxygen,” came the response from the assembled recruits.
“That’s right, it didn’t have that air,” Studds said, turning back to gesture at the rapidly failing “house” as Webb stepped aside to give the recruits a closer look in the second-floor window.
“Now that we’ve opened that back up, it’s drawing in that cool air from down low here and it’s got a place to go now,” Studds said, pointing at the fire as the flames climbed steadily up the “stairwell” toward the open window on the second floor. “See how it’s moving straight across? Right into that path of least resistance.”