Fire engulfed portions of the historic Irving Junior High School on Wednesday for the third time in less than six months.

"I'm so sick of this, I can't see straight!" Salt Lake Battalion Chief Gordon Nicholl said, referring to the hundreds of hours spent by firefighters battling intentionally set blazes in the building at 1200 East and 2100 South.Firefighters knocked down flames at the building three weeks ago. That fire was set in the school's west wing, burned upward, damaging classrooms on the second floor and partially gutted the third floor.

Wednesday's fire was set on the third floor and destroyed three rooms, finishing off was left on that floor. More than 20 firefighters battled the blaze for 30 minutes before controlling it.

"Whoever is doing this and continues to do it will eventually injure or kill one of our firefighters - and then they'd better be prepared to face arson charges and a murder charge," Nicholl said.

The school's gymnasium, east and central wings were gutted during a fire last November that caused $500,000 damage. Explosions during the intenblaze leveled several walls.

Nicholl said investigators believe more than one person is involved in the fires at the 70-year-old building.

And the constant smoke and flames have translated into bad business for retail shops near the school.

Gart Brothers Sporting Goods, 1175 E. 2100 South, has had to endure smoke from the burning building and fire trucks have blocked access to the store's parking lot for several hours at a time.

"It makes business slow; you get real tired of it," assistant manager Dave Namba said.

Fire officials will likely petition Salt Lake City government to condemn the building as a "public nuisance," Nicholl said.

"It was a grand building in its day, but in my opinion it's time for a bulldozer," he said. "It's a dangerous building and the law of averages is going to catch up to us; one of our firefighters will be injured or killed in if we continue to fight fires in there."

The building is listed on the national and state historic registers and was remodeled before the November fire at a cost of $3.5 million.

Nearly all of its floors were hardwood, and the ceilings, adorned with intricate artwork, were 12-feet tall.