A PASS device can be set off manually or will go off automatically under which circumstances?

A Personal Alert Safety System (PASS) device is designed to enhance firefighter safety by providing an audible alarm when a firefighter becomes unresponsive or immobile. The device works primarily by detecting motion; after a period of inactivity—usually about 30 seconds to a minute—it will activate the alarm automatically. This feature is crucial in emergency situations where a firefighter may become incapacitated and unable to signal for help.

The design of the PASS device focuses on the movement of the wearer, which ensures that those operating in hazardous environments are alerted if any team member is in distress. This automatic activation is vital for protecting firefighters during operations where rescue may be necessary.

While the other options suggest scenarios involving gas detection, temperature changes, or submersion, these are not functionalities of a typical PASS device. In essence, the right answer focuses on the device's primary function related to motion—when it becomes motionless for a set period of time, it triggers the alarm to indicate a potential emergency situation.