What activates the vibralert low air alarm?

The vibralert low air alarm is designed to activate when the air supply in a SCBA (Self-Contained Breathing Apparatus) cylinder drops to a specific pressure level, which is typically set at 1830 PSI or approximately one-third of the tank's capacity. This feature serves as an important safety mechanism for firefighters and emergency responders by providing a tactile alert to the wearer that the air supply is getting low and that they should begin to proceed to a safe area for replenishment or change of air supply.

The choice indicating reaching 1000 PSI does not trigger the vibralert, as it is above the designated alarm pressure. An empty air tank would mean the alarm has already been ignored too late, as responders should be aware of their air supply well before reaching empty. Additionally, an exceedance of temperature, such as 300°F, is not pertinent to the low air alarm but rather relates to equipment safety and functionality. Thus, the choice that accurately reflects the operational threshold for activating the vibralert low air alarm is the one indicating a drop to 1830 PSI or one-third tank.