What is the minimum air pressure that should be shown on an SCBA gauge before use?

The minimum air pressure that should be indicated on an SCBA gauge before its use is 90% of the cylinder’s rated capacity. This ensures that the SCBA will provide adequate air supply for the duration of the intended operations, maintaining the safety and effectiveness of the breathing apparatus in hazardous environments.

Using the SCBA below this threshold could compromise the responder's safety, as it may not provide enough breathable air for the expected duration of the task. This is particularly critical in emergency situations where the user may encounter unforeseen delays or challenges. Therefore, having 90% of the rated capacity ensures a sufficient safety margin.

Other options, while they might suggest maintaining a certain level of air pressure, fall short of providing that crucial buffer needed for safe operation in potentially life-threatening atmospheres.