When is the EOSTI or low-air alarm constructed to sound?

The low-air alarm, also known as the Emergency Operation Standard for Tactical Intervention (EOSTI), is designed to sound when the air pressure in a self-contained breathing apparatus (SCBA) cylinder reaches a critical level that indicates a low air supply. The correct answer is when air pressure is at 35%.

This threshold is established to ensure that firefighters have adequate warning to exit a hazardous environment before they run out of breathable air. By triggering the alarm at this level, it helps to allow sufficient time for the firefighter to assess their situation, make decisions about their safety, and take appropriate action to exit the incident scene or to find a place to refill their air supply.

Other options indicate different pressure levels, but 35% is the specifically designated standard that balances safety and practicality, ensuring that firefighters are alerted early enough to maintain their safety while effectively carrying out their duties.