When will an EOSTI sound?

The Emergency Open-Space Transmit Indicator (EOSTI) is designed to provide critical alerts regarding the operational state of equipment used in emergency situations, particularly in wildland fire environments. One of its key functions is to alert personnel when the air supply in a breathing apparatus cylinder drops to a critical threshold.

The sound from the EOSTI is specifically programmed to activate when the cylinder level reaches 25% capacity. This alert serves as an important safety feature, ensuring that firefighters or rescue personnel are aware that their air supply is low and that they need to exit hazardous areas or take appropriate action.

While an activation signal might occur at full capacity or in the event of a malfunction, those situations do not trigger the specific alert provided by the EOSTI regarding low air supply. Hence, the timing of the alert at 25% remains the critical function of the EOSTI, making it essential for the safety of operating personnel in the field.