When does the emergency pressure side activate?

The emergency pressure side activates when the cylinder pressure drops to one-third of the supply. This mechanism is crucial for ensuring that firefighters have access to a backup supply of air when the primary air supply is running low. By setting this threshold, it ensures that there is an alert to the users that they need to either conserve their air or prepare for an alternative breathing apparatus.

This option is appropriate because monitoring the cylinder pressure and activating the backup at one-third of the supply helps prevent unexpected loss of air during operations, allowing users to work more safely and effectively in emergency situations. It serves as a proactive measure, rather than waiting until the cylinder is empty or reaches a much lower pressure.