"It was a difficult fire to fight because inside the storage sheds people had a lot of stuff compacted down," he said.
Most of the last three storage units of the building were saved, he said.
One firefighter suffered a dislocated thumb, but there were no other injuries even though the building and its contents posed several dangers, Barbuzanes said.
Ammunition stored in one unit was popping and going off from the heat of the fire, he said.
Two vehicles - a Corvette and an old Ford pickup truck - were parked in the building he said.
"We're lucky no firefighters were seriously hurt," Barbuzanes said.
Contents of the storage units also included antique furniture, a baseball card collection and other valuable personal property, he said.
Firefighters were at the scene until 7:30 a.m.
A Pennsylvania State Police fire marshal arrived to inspect the damage to determine the source and a cause of the fire, which was labeled suspicious.
Two barns owned by Thomas Steiger Sr., a Mercersburg attorney, burned in July and August. Both fires were being investigated as arsons.
Surveying the charred remains of the building and its contents, owner Tom Gift III of Chambersburg, Pa., who was called to the site soon after firefighters arrived, said he considers it a total loss.
The building was insured but damage estimate had not been determined.
Gift began construction of the storage facility last September and the first tenant moved items in on Jan. 1, he said.
Most of the renters were local, with some from Hagerstown, Gift said.
"I'm not sure what I'm going to do. Just clean up as soon as we get the OK," he said.
Gift said he'll probably build another storage facility to replace the burned one.