What Is the Yellow Knob in a Gas Fireplace?

Function

• Supply gas shut-off valves are manual devices installed on your natural gas or liquid propane appliances as a safety precaution, and they may or may not have a yellow knob or switch that controls them. Some gas shut-off valves are brass, and are operated with a valve key, which is a device that fits into the slot on top of the valve to turn it. Whether you have a yellow knob or a brass slot, the function is the same. They are connected to the gas line leading into your appliance to temporarily shut off the gas supply for maintenance or in the event that you can’t reach or shut off the main gas supply.

Main Gas Valve or Supply Valve

• Gas appliances are typically installed with two shut-off valves. One is the main valve, usually red and located outside the home, and the other is a supply shut-off valve, which is located inside on the supply pipe and within 6 feet of the appliance to which it is connected. There should be one gas supply shut-off valve per gas appliance in your home, and these must be installed by a qualified technician. One supply shut-off valve should never control more than one appliance.

Operating Gas Supply Shut-off Valves

• The shut-off valve may not be labeled to allow you to see whether the gas is off or on, so it’s important to know how to operate it. The control for the valve has either a flat yellow blade on top of the knob, or, in the case of a brass control valve, it will have an arrow or slot. When the knob is turned so the handle or slot is in line or parallel with the supply pipe to which it is connected, the gas is on. When it is turned so that the handle or slot runs across or perpendicular to the pipe, the gas supply is off.

When to Close Supply Gas Shut-off Valves

• The supply shut-off valve should only be closed under certain conditions. If you suspect a gas leak or the fireplace requires service or maintenance, shutting off the supply gas valve is usually sufficient. If you suspect a leak, evacuate your home as soon as you shut off the gas, and contact the fire department and your gas company from a neighbor’s home. The gas supply valve should only be turned on again in this case if you have detected and fixed the source of the gas leak. If you have appliances other than your fireplace that are fueled by natural gas or propane, the gas should be shut off at the main supply valve when a leak is suspected.