Smell rotten eggs? If you suspect a gas leak, leave immediately and take others with you. DO NOT do anything that could create a spark, such as light a match, smoke, use the phone, turn lights or appliances on or off, or start a car. Once outside, call 1-800-75-CONED (1-800-752-6633) or 911 to report the leak. National Grid customers should call 1-718-643-4050. Don’t assume someone else has already called. You can report a leak anonymously.