Acceptable accuracy of monitor readings is assured by

The correct answer emphasizes the importance of regular calibration to ensure the accuracy of monitor readings. Calibration is a critical process that involves comparing the readings of the monitor with a known standard and making necessary adjustments. This practice is essential because environmental conditions, sensor drift, and the aging of equipment can affect the performance of monitoring devices over time. By calibrating the monitors regularly, you maintain their accuracy, ensuring that the readings reflect true values, which is vital for safety in confined space situations.

While using multiple monitors can enhance safety by providing cross-verification, or replacing monitors may ensure that you have the latest technology, these measures alone do not guarantee the accuracy of the readings. Calibration, on the other hand, directly addresses the reliability of the data being collected. Thus, regular calibration is the key to ensuring monitor accuracy effectively.