Make sure you know where your shutoff valves are for all of your gas appliances, ie fireplace, stove, furnace & water heater. If you ever smell a gas leak, immediately turn off any and all gas shutoff valves in your home and contact a qualified HVAC or plumbing contractor & your local gas company, so the leak can be quickly identified and repaired.
Now is also a great time to schedule a service call for your furnace before we get into really cold weather!
P.S. the gas is ON!