Place the lawn mower on level ground so it won't move when you're refueling the gas tank. Remove the fuel cap and slightly tip your gas can until gas begins to flow out. Don't pour too fast or you might overflow the tank, if you're not careful. Once the tank is full, firmly twist the fuel cap back on.
Fuel leaking from the gas tank can catch fire if it contacts a hot surface or is exposed to any spark that occurs near the engine or the blades, especially if the blades contact a rock or hard surface. You can often smell gas if it's leaking from the tank of your lawn mower. If you smell gas while operating your mower, stop immediately and check for leaks around the fuel tank. Also check the fuel lines to ensure they are not leaking.
Always make sure the gas cap on the fuel tank is securely tightened. If not, the gas can slosh around in the tank while you're mowing, and possibly leak out from the gas cap. Secondly, check the structural condition of the fuel tank and fuel lines often. If you notice excessive amounts of wear or rust, you should replace the tank before it begins to leak.
Cleaning up small gas leaks or spills is important; use some shop towels and rags to wipe up the surface spills. You can also use saw dust or kitty litter to absorb gas on the ground. Take gasoline-soaked material to your local hazardous waste center for proper disposal.