What is a critical factor to check when operating a gas detector?

The calibration of a gas detector is a critical factor to check when operating the device. Calibration ensures the accuracy of the readings the detector provides. It involves adjusting the instrument to identify gas concentrations correctly, allowing for reliable monitoring of gas levels in the environment. A properly calibrated detector guarantees that it responds appropriately to specific gas concentrations, thereby facilitating proper safety measures.

While the other options may be relevant to gas detection in specific contexts, they do not hold the same immediate importance as calibration. The type of gas being detected pertains to understanding what hazards might be present but doesn’t directly impact the functioning of the detector itself. The date code can provide information about the detector's lifespan or expiration but does not affect its operational capability on a day-to-day basis. Monitoring the pressure of the gas supply might be crucial for overall system performance but isn't directly related to the operation of the gas detector concerning accurate readings and responses.