Carbon dioxide (R744) is often used in the low-temp side of cascade systems. Due to the pressure-temperature relationship of R744, it would be cost prohibitive and unnecessary to meet all the design pressure requirements of Section 9.2 for refrigeration systems using R744, since the required standby pressures for R744 are much higher than those experienced during normal operation. The proposed change allows R744 as a secondary coolant or refrigerant in certain situations, permitting limited releases to the atmosphere during unusual events, such as an extended power failure with coincident heat gains that raise system pressures.