Low-pressure acetylene gauges usually have a red line to indicate dangerous pressure levels above ____.

Low-pressure acetylene gauges are designed with safety in mind, especially given that acetylene gas can be hazardous under certain conditions. The red line typically indicates the maximum safe operating pressure to prevent dangerous situations such as flashbacks or explosions.

The correct answer is associated with 15 psig (103.4 kPa), which is the pressure above which acetylene becomes unstable and poses risks when handled improperly. If the gauge indicates pressure beyond this threshold, it signals the user to take immediate corrective actions to reduce the pressure to safe levels. Maintaining acetylene pressure within safe limits is critical for both safety and effectiveness in various welding processes.

Understanding this range helps ensure that operators remain within safe operating conditions, minimizing the potential for accidents and enhancing the overall safety of welding practices.