Gas piping comes in a variety of materials, but the most common one in households is black steel. The length of the gas pipes may also affect gas flow - the longer the pipe, the lower the air flow. When in doubt, hire a home service pro to get the job done.
John was quick to respond, stayed in touch as we rescheduled, and then quickly diagnosed and fixed the problem with our humidifier on the furnace. We wanted someone to handle our annual maintenance needs for all HVAC and our experience...