Which component of SCBA warns when the system is reaching 20-25% of cylinder capacity?

The component of the Self-Contained Breathing Apparatus (SCBA) that indicates when the system is reaching 20-25% of cylinder capacity is the end of service time indicators (EOSTI). These indicators are designed to alert the user that their air supply is running low, ensuring that they can safely exit hazardous environments before running out of air. The EOSTI is vital for maintaining safety standards during firefighting and rescue operations, as it allows for timely decision-making about retreating to a safe area before the air supply is depleted.

While other components like the pressure gauge and low-air alarm provide important information about the SCBA's status, they do not specifically indicate the 20-25% threshold. The pressure gauge displays the current pressure in the cylinder, which helps users estimate their remaining air supply, but doesn't provide an automated alert based on a preset percentage. The low-air alarm warns users of low air pressure, but typically activates at a higher threshold, not specifically at 20-25%. The flow indicator shows the flow of air coming from the SCBA but does not inform the user of the specific level of air remaining in the cylinder.