Customer called in needing a gas pressure test. Gas company shut their gas off because it was not holding pressure. Upon arrival found that business has 4 rooftop units. Each valve is in the open position and each unit has a diaphragm that doesn’t allow certain of psi to build up. Went ahead and isolated all 4 rooftop units and performed an air pressure test to only the gas line for business unit. Gas meter for business is the far right one. Pressured gas line to 15psi. Gas pressure held for over 30 minutes & pressure did not drop once. Went ahead and called customer that air pressure held just fine and they can call gas company to turn gas back on for them. After gas company turns gas back on, need to turn on all for 4 rooftop units gas back on.