"Obviously, when you are in a work harness for that length of time, that's not a healthy position," said Lower Providence Township Fire Department Chief Bryan McFarland.
McFarland attributed the accident to a "malfunction" of equipment. He did not elaborate.
The U.S. Occupational Safety and Health Administration was investigating the incident.
The workers’ employer, Corrosion Control Corp., of Pedricktown, New Jersey, does have an OSHA history, said Joanna P. Hawkins, deputy regional director for the U.S. Department of Labor in its Philadelphia office.
In 2008, a company employee who was sandblasting died at a Philadelphia location, and OSHA assessed an $18,000 fine, records showed.
Unlike in this instance, however, the worker at the Philadelphia site wasn't wearing a harness.
About 50 emergency workers participated in this afternoon's rescue.
From a crane platform near the top of the tower, one of the rescuers lowered himself into the tank. He managed to pull the workman to the rescue rope, and the two slowly worked their way to the bottom.
He was removed from a manhole-size opening at the base of the tower.
McFarland said the man was conscious throughout the ordeal and that although he was able to talk, the acoustics inside the tank made his words indecipherable.
Among those who participated int he rescue were the Lower Providence Police and Fire Departments, along with crews from King of Prussia and Plymouth Township, were on the scene. At least a dozen emergency response vehicles also were at the scene.
The deceased worker has been identified by co-workers but his his name has not been released, said Montgomery County Coroner Walter Hofman.
He said an autopsy would be performed tomorrow morning.
Contact Aubrey Whelan at 610-313-8112 or at email@example.com, or follow @aubreyjwhelan on Twitter.