A Valley Metro bus fire that created dramatic flames shooting into the sky Monday night on Loop 202 off-ramp demonstrated how compressed natural gas safety systems are designed to work, according to experts. The bus used compressed natural gas, which contributed to the intensity of the flames that firefighters from Tempe and Phoenix encountered when they surrounded the bus. David Clement with CNG Services of Arizona said compressed natural gas actually requires a higher temperature to ignite than unleaded gasoline or diesel fuel…