If you smell gas in your home, the first thing you should do is call 911. Then call the gas company. You should have the number stored on your phone. The gas company will send somebody out—an emergency responder or someone on call to assess the situation—to try and detect where the leak is coming from. If determined safe to enter your mechanical room, here are your next steps to turn off your main gas line if you were instructed to do so.
In single family homes, when the gas line is on, its handle is parallel with the gas line. Turn the handle 90 degrees perpendicular to the gas line. This shuts off the gas supply to the house.
In townhomes, you don't have this option. Your shut off valve is on your gas meter outside. We recommend leaving your home and calling 911.
A strong egg-like odor typically means a severe leak. Remember, safety is your number one concern. While some leaks may be localized gas leaks—like just in the kitchen—it is always safer to completely shut off the valve and let the firefighters check the home. Once safe to re-enter, you will probably need to relight the pilot light to your water heater and reset the furnace if the heat was running.