What must be done in case of natural gas leakage?

Building entrance floor and all windows opening to bright field must be opened in order to ventilate the place. Main natural gas input valve at building entrance must be switched off. Open flames must be put out. You must not strike matches, flick lighters or smoke. Electric devices must not be operated. They must not be turned off if they are in operational state. You must immediately inform the natural gas company or the dealer, which has built the installation, or authorized service. Natural gas emergency number is: 187. Phones of the building having natural gas leakage must not be used in any case. Push buttons and door bells must on no account be used. Building manager must be informed. Elevators and similar devices must be operated.