ALLENTOWN, Pa. – Many are saying the large fire that consumed Allentown’s Front Street last week is the largest the city has seen in years.

You may have often heard it referred to as a 6-alarm fire. But what exactly does that mean?

In short, officials say, it means it was a massive fire with dozens of units requested in six separate calls or alarms raised.

“That was probably one of the biggest fires I’ve seen,” Battalion Chief Roger Scheirer with the Catasauqua Fire Department, said. “I haven’t seen that in 20 years in the city. And I’ve been on some big fires in Allentown.”

For each alarm, there’s a pre-planned set of stations and/or equipment on standby.

“The alarm is an easy way to signify that we need more assistance,” Cpt. Jonathan Hammel, with the Allentown Fire Department, said. “And that assistance could either be apparatus or personnel.”

So, for example, the first alarm alone:

“Is three engine companies, one truck company, which is a ladder company, essentially the battalion chief, and an extra engine to stand by as the rapid intervention team,” Cpt. Jonathan Hammel, with the Allentown Fire Department, said.

Now, imagine five additional calls after that one.

“When we go to a second alarm…for Allentown, that brings you two more engine companies and our second ladder company,” Hammel said.

During last week’s 6-alarm, of the 200 firefighters in 21 departments rushing in to help, Catasauqua was one of them.

“We go on standby here at our station on a second alarm fire for the city of Allentown,” Battalion Chief Scheirer said.

Scheirer says his Catasauqua crew was able to arrive in Allentown within minutes, all because of the alarm system in place.

“We move into the city on a third alarm and then we go to the scene on a fourth alarm,” he explained.

So then if all of Catasauqua’s volunteer fire fighters are battling the big blaze in Allentown, who’s holding down the fort in Catasauqua? The answer goes all the way out to Carbon County.

“We had Palmerton down here covering us during the 6-alarm fire,” Scheirer said.

So then, if Palmerton Fire is in Catasauqua, who would fill in for Palmerton? Scheirer says they may keep some folks behind there or get other stations to cover them. And so on and so on.

Hammel tells 69 News until recently, the system only went up to three alarms, and if more help was needed, each individual call would be made separately after that.

“Like we would select, I need two more truck companies, or I need three more engines,” Hammel said. “But what we’ve done now is the folks that have worked on this, they’ve built it out so that on every extra alarm it brings a set number of apparatus with that whole project.”

Captain Hammel says the department has also raised the bar on expectations on what the planned mutual aid will bring in when helping out in Allentown, including services like CPR and first aid.

Captain Hammel says the alarm system keeps Allentown Fire running like a well-oiled machine: officials noted there were no deaths or injuries to the general public in this large, devastating blaze.

“I think it’s pretty extraordinary that we had one minor injury to one of our members,” Hammel said.