A method is provided for connecting a secondary source of a medical gas to a control panel of a medical gas supply. The control panel is connected in the system fluidly between primary supply sources holding types of medical gas and gas outlets for the delivery of the respective types of medical gas to devices in a medical facility. For each gas type, the control panel houses a respective shut off valve. The shut-off valve may be closed to isolate the upstream source from the downstream components. A fitting is installed in place of an existing pressure gauge in the control panel. The fitting provides ports for at least one gas specific DISS coupler and further components such as a pressure gauge and transducers. The fitting has a configuration such that when installed, the fitting does not interfere with closing the cover to the control panel.