Each appliance shall be connected with a ground joint union or an approved flexible connector. Appliance connectors shall, at no time, have a diameter less than that of the inlet connection to the appliance as provided by the manufacturer.
No part of the flexible connector shall be concealed within or run through any wall, floor, or partition. (NFPA 54 9.6.2 [1c])
Gas-burning appliances shall be rigidly connected to the gas piping system with steel or wrought iron pipe and malleable iron fittings, except as noted below.
Gas appliances, except for room heaters and gas logs not secured in a fixed position, may be connected to the rigid gas piping with listed metal flexible double wall non-corrosive connectors or single wall stainless steel connectors with an approved shut-off valve used between the gas-supply outlet and such connector. The flexible connector shall not exceed 3 feet in length, except range or dryer connectors, which may be 6 feet in length, and connector is of adequate inside diameter to pass the required appliance load.
All connectors shall be of such size as to provide the total demand of the connected appliance, based on rated appliance input. Flex connector capacities may vary with manufacturer, see listing tag on connector for capacities.
The connection of an indoor appliance with any type of gas hose is prohibited, except when used with laboratory or shop equipment or equipment that requires mobility during operation. Such connections shall have the shut-off valve installed at the connection to the building piping.
When gas hose is used it shall be of the minimum practical length, but not to exceed six (6) feet, except for hand torches and special mobile equipment, and shall neither extend from one room to another nor pass through any walls, partitions, ceilings, or floors. Under no circumstances shall gas hose be concealed from view or used in a concealed location. (NFPA 54 9.6.2 [1c])
Outdoor portable appliances may be connected with an approved outdoor hose connector not to exceed fifteen (15) feet in length provided it connects outdoors to approved gas piping and approved shut-off valve connected to the rigid gas piping.
Only listed gas hose shall be used and only in accordance with its listing. Gas hose shall not be used where it is likely to be subjected to excessive temperatures (above 125 degree F) nor shall it be used as a substitute for a standard appliance connector.
Appliances may be connected to the fuel gas piping by means of an approved listed quick-disconnect device with an approved shut-off valve connected to the rigid gas piping.
Outdoor gas barbecues may be installed using polyethylene tubing, provided the tubing is buried and connected to wrapped iron pipe 3 feet outside of the building and at a depth not less than 18 inches below grade. A wrapped steel riser is used when the connection is brought above grade. A shut-off valve shall be installed on the riser before connections are made to the barbecue.