What firefighters don't know can kill them. Dangerous alterations to buildings have been cited as a factor in at least 13 FDNY line-of-duty deaths since 1991—most recently, the Deutsche Bank disaster. Since then, the department has stepped up inspections, ordering fire companies to perform their three-hour building-inspection shifts three times a week instead of two.

What firefighters—and city building and fire inspectors—don't know can also kill civilians. Hence the outrage over the Bronx fire in April that killed a family in a building that had been the target of complaints about illegal conversions. That tragedy led City Hall to establish a new task force for improving inspections and compliance. City Council members, frustrated by the inability of inspectors to get access to the buildings they want to check, pushed for more aggressive moves.

But there's more to improving building safety than political will. Robert LiMandri, the city's buildings commissioner, pointed out at a June hearing that inspectors have to wield their power carefully, given the considerable value that American law places on a person's right to privacy in their home. What's more, investigating illegal conversions is "very resource-intensive," the commissioner said. If someone bars their door to inspectors, he said, it's hard to amass enough evidence to justify going to a judge to get a search warrant—and even when this is done, more than half of inspections fail to turn up evidence of a violation. Sometimes what appears to be obvious evidence of illegal apartments is nothing of the kind: An extra gas meter could mean there's an illegal unit or simply that there's a separate meter for a building's common area. Plus, addressing illegal conversions—which reflect the city's tight housing market—can mean evicting a family onto the street, which is far from an ideal outcome.

Three New York agencies inspect housing: the buildings department enforces the building code, the Department of Housing Preservation and Development wields the housing code, and the fire department enforces the fire code, using both fire companies and a separate staff of civilian fire inspectors, who are unarmed peace officers. There are more than 975,000 buildings in New York. "It's a very, very big city," says Robert Unger, counsel to Local 2507, the union for uniformed EMTs, paramedics, and inspectors. "Frankly, we can never have enough inspectors."

Meanwhile, uniformed firefighters are chafing under the orders to do more inspections—even though this move came as a response to two FDNY deaths. Both the firefighters' and fire officers' unions have filed grievances opposing the city's unilateral move to increase inspections, which the unions say violates their contracts. More substantively, the unions say their members have not been adequately trained to do inspections. In 2010, Gov. David Paterson vetoed—at Mayor Bloomberg's request—a bill that would have required that firefighters be provided with 80 hours of inspection training, at a cost of $29.5 million a year. The Citizens Budget Commission called the training a "laudable goal" but dubbed the bill "unnecessary and financially burdensome."