Section 108.445 - Alarm and means of escape(a) Each CO2 system that has a supply of more than 136 kilograms (300 pounds) of CO2 , except a system that protects a tank, must have an alarm that sounds for at least 20 seconds before the CO2 is released into the space.(b) Each audible alarm for a CO2 system must have the CO2 supply for the system as its source of power and must be in a visible location in the spaces protected.