What might cause a difference between the SCBA bottle gauge and the regulator gauge?

The answer highlighting differences in measurement units is derived from the understanding that gauges can be calibrated differently. If the SCBA bottle gauge measures the pressure in PSI and the regulator gauge is designed to show the air supply as a percentage, there will inherently be a discrepancy in the readings. This distinction between measurement systems underscores the importance of interpreting gauge readings correctly, especially in critical safety environments like fire response.

To clarify further, the chosen answer reflects a fundamental principle in instrumentation: the units of measure must align to ensure accurate comparisons. When pressure is measured in one unit (PSI) and the remaining capacity is in another form (percentage), it creates an apparent divergence in the readings that would otherwise align if standardized units were used.

In contrast, other options address distinct issues. A leak in the bottle would result in a gradual loss of pressure affecting both gauges but would not inherently create a differential reading when calibrated correctly. An overloaded bottle might compromise safety but wouldn't directly account for gauge discrepancies in readings if both are functioning properly. Similarly, a malfunctioning regulator could cause pressure issues, yet it would not be the root cause of a difference tied to measurement units. This context aids in understanding how operational variables in equipment readings must be considered to ensure proper safety protocols in the field