High heat may cause malfunctions in the personal alarms firefighters carry to signal if they go down in a fire, a federal report has disclosed.

Some of the devices, which are designed to emit ear-splitting beeps if a firefighter stops moving for more than 30 seconds, fail in temperatures above 500 degrees Fahrenheit, while others become quieter, the report by the National Institute of Standards and Technology said.

Firefighters regularly encounter temperatures of 1,500 degrees Fahrenheit.

Nationally, at least 15 firefighter deaths have been linked to the malfunction of the devices, including one in New York City, Senator Schumer said at a news conference to bring attention to the 2006 report yesterday.

“Every single firefighter who goes into a fire could be at risk,” Mr. Schumer said.

The devices, known as Personal Alert Safety Systems, are about the size of a deck of cards and are intended to help first-responders locate firefighters who fall unconscious or get pinned inside a burning building.

The family of firefighter Thomas Brick, who died inside a burning mattress factory in Inwood in 2003, filed a lawsuit against the city in 2005 alleging that the failure of his alert system contributed to his death.

The vice president of the firefighters union, James Slevin, said the fire department had been aware of possible problems with the devices since Mr. Brick’s death.

“It wasn’t what killed him, but it was believed there was a problem with the PASS device,” Mr. Slevin said.

Mr. Schumer said he did not blame the New York City fire department, but said instead he would call on federal agencies and private manufacturers to inspect old devices and improve new ones.

A fire department spokesman, Jim Long, praised Mr. Schumer’s efforts to improve firefighters’ equipment.

“We have the best PASS equipment available,” he added.