PASS device

A PASS device (personal alert safety system), also known as a distress signal unit (DSU) or ADSU (automatic distress signal unit), is a personal safety device used primarily by firefighters entering a hazardous or "immediately dangerous to life and health" (IDLH) environment such as a burning building.

On a fireground, the sound of an activated PASS device indicates a true emergency and results in an immediate response to rescue the firefighters in distress.

Older models of PASS devices required manual arming by firefighters prior to entering a dangerous environment.

This style devices are powered by battery, are easily activated while wearing gloves, and are intrinsically safe to operate in flammable or explosive atmospheres.

It was reported that shortly after the events of September 11, 2001, the sound of many activated PASS devices could be heard beneath the rubble of the collapsed World Trade Center.

PASS device (22, boxed in red) integrated into an SCBA unit. It is connected by a hose (18, green) to the air circuit and arms automatically when the air circuit is opened.