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No one imagined the way careless smoking spiraled into a deadly inferno in a toxic ground zero bank tower, so three construction-company supervisors shouldn't be blamed for it, defense lawyers said Tuesday as their manslaughter trial neared an end.

"This was a horrible, perfect storm of bad circumstance" in a condemned building rife with unexpected perils, attorney Edward J.M. Little said in a closing argument.

The two firefighters killed in the August 2007 blaze at the former Deutsche Bank building "died horrible deaths, but it wasn't because of anything the defendants did," Little said. He represents Jeffrey Melofchik, who was the building's site safety manager.

Melofchik, toxin-cleanup director Mitchel Alvo and asbestos-cleanup foreman Salvatore DePaola are the only people criminally charged in the fire, which revealed a roster of missed inspections, fire hazards and regulatory oversights at the building. It was being dismantled after being damaged and contaminated with toxic debris in the Sept. 11 attacks.

The John Galt Corp., which employed Alvo and DePaola, also is charged with manslaughter.

Prosecutors say the men knew a crucial firefighting water pipe had broken in the building's basement months before the fire, didn't fix or flag the breach and even concealed it.

"The defendants knew that this building was, in essence, a deathtrap," Manhattan assistant district attorney Bryan J. Fields said in his opening statement in April. Prosecutors haven't yet given their summation.

Firefighters found themselves unable to get water on the flames for about an hour as the blaze built on upper floors, filling some with thick black smoke that made it impossible to see, firefighters testified.

Firefighters Robert Beddia, 53, and Joseph P. Graffagnino, 33, died after being trapped in the smoke and running out of air in their oxygen tanks.

Defense lawyers say the men didn't realize the broken pipe's importance in a basement laced with pipes. "There was no conspiracy among these people to conceal or do anything," DePaola's lawyer, Rick J. Pasacreta, told jurors in his summation Tuesday.

And the disaster was fed by a litany of hazards beyond the men's control, their lawyers say. To contain toxins, regulators had given their OK to stairwell barriers that slowed firefighters' progress and a fan system that ended up keeping smoke in and pulling it down instead of letting it rise and escape.

Even if the firefighting pipe, called a standpipe, had been working, it wouldn't have made a difference, Little argued.

"It was literally hell up there," he said. "They were trapped in circs that they didn't know anything about, that they could not have foreseen . and it's speculation and an illusion to say, 'If only they had water at (the early stages), none of this would have happened.' They still would have run out of air..

"Nothing could have happened except that firefighters were going to die," he said as about a dozen uniformed firefighters watched from the courtroom audience.

After the deadly blaze, the city and Melofchik's employer, general contractor Bovis Lend Lease, acknowledged mistakes. Bovis agreed to finance a $10 million memorial fund for slain firefighters' families, and the fire department created dozens of inspection and auditing jobs, among other responses.

If convicted, Melofchik, 49, DePaola, 56, and Alvo, 59, could face up to 15 years in prison. The Galt company, which also is charged, could face a $10,000 fine.

Alvo and the company have elected to have a judge decide their cases. A jury will render a verdict for the others. The judge and jurors heard testimony simultaneously, with the judge getting some additional evidence, during a roughly 10-week trial.

Closing arguments were expected to continue through Wednesday.