Most gas leaks are caused by leaving an appliance in an unsafe condition, so…
Do not leave heaters on but not running without checking the gas supply.
Do not sleep without turning off the gas appliance valve as well as the main gas supply line lever.
Avoid using very old or broken heaters and pipes.
Ensure the gas heaters and gas lines are properly installed with no leaks.
Advise children and adults not to do anything during a gas load-shedding that may cause a gas explosion, such as lighting a match, operating an electrical switch, even using a telephone in the building.
Immediately vacate a room or house when you suspect a gas leak.
Call SNGPL on (051) 9257710-11 and (051) 9257713-19 to check gas supply lines if you suspect a leak. Source: Internet