What button should be pressed to illuminate the primary screen?

To illuminate the primary screen of the MSA G1 Self-Contained Breathing Apparatus (SCBA), the correct action is to press the RESET button. This button is specifically designed to refresh and activate the display, allowing the user to clearly view critical information about the SCBA’s status, including remaining air supply, battery condition, and other essential operating metrics.

The function of the RESET button is essential in situations where the display may need to be reactivated due to inactivity or if it has gone into a low-power mode. Pressing this button serves to ensure that the operator has immediate access to the vital information necessary for safe and effective operation of the SCBA, particularly in hazardous environments.

Other options, such as the "Start" button, are typically related to initiating systems or functions but do not directly address illuminating the main display. The "Light" button, usually found on devices to activate a flashlight or other illumination features, does not specifically illuminate the primary screen. "Power" usually controls the overall power state of the device rather than specifically focusing on the display. Thus, the RESET button is the key to shining a light on the information essential for the user’s safety and operational effectiveness.