LPG Leak, What Would You Do?

Electricity and Magnetism Level 2

James arrived home after a party and realized that he had forgot to turn off the knob of the gas line. There is a strong smell of liquefied petroleum gas in his apartment.

What should he do to avoid any accidents?

Turn off the knob of the gas line.
Open all the windows.
Turn on the exhaust fan.
Turn off all the electrical appliances.