According to NFPA 54, which component must be upstream of each gas pressure regulator?

The requirement for a manual gas shutoff valve to be installed upstream of each gas pressure regulator is emphasized in NFPA 54 regulations to enhance safety and control over the gas flow. This valve provides a means for emergency shutoff, allowing personnel to quickly and effectively interrupt the flow of gas in the event of a leak or other emergency situations.

In contrast to the other components mentioned, while a gas meter measures the quantity of gas consumed and a gas monitor detects unsafe levels of gas, neither are primarily designed to control the gas supply directly in emergencies. An automatic shutoff device can provide added safety by closing off gas flow when certain dangerous conditions are detected, but it is not mandated specifically to be located upstream of the gas pressure regulator in the same way a manual shutoff valve is. Thus, the necessity for the manual shutoff valve aligns with best practices for ensuring safety and facilitate maintenance operations without compromising the integrity of the gas system.