According to NFPA 54, what must an automatic shutoff device do when downstream pressure reaches a maximum specified value?

The requirement for an automatic shutoff device, as stated in NFPA 54, is to close and remain closed until manually reset when the downstream pressure reaches a specified maximum value. This function is critical for ensuring safety in gas systems. If the pressure exceeds this threshold, it can indicate a potential safety hazard, such as a malfunctioning regulator or a leak in the system. By closing off the gas supply, the device prevents further gas flow, thereby mitigating the risk of an explosion or fire.

This design emphasizes the principle of safety in gas management; once the shutoff device activates, it requires a manual reset to ensure that a qualified individual has assessed and resolved the underlying issue before gas can flow again. It reinforces the importance of human oversight in addressing pressure anomalies rather than allowing systems to operate automatically without proper checks.

In contrast, while providing alarms or notifications can serve as useful safety measures, they do not directly prevent further gas flow, hence would not fulfill the primary function required by NFPA 54 in this context.