In the event of an evacuation:

• Turn the cylinder OFF (off is clockwise) on the top valve. Turn off all gas appliances.

• Leave cylinder in its current location. Be sure that it is upright and on a secure base so it does not fall over. Make sure there that are not combustible materials near the cylinders.

• Make sure the pressure relief valve is facing away from the building (below the valve, normally has a plastic cover, located on the opposite side of where the gas line screws into the cylinder)

• BBQ and Forklift cylinders need to be moved away from any wooden structures including BBQs (as should the BBQ itself).

• Cylinders should never be stored indoors or under a property. 
  

• Do not attempt to keep cylinders cool with wet cloth or material; these will dry out and may be combustible.

During a Bushfire:

During a fire, the heat will increase the pressure inside the cylinder causing the safety valve to activate to protect cylinder integrity. A loud hissing noise may be heard and a flamethrower effect may be seen coming out from the safety valve. When the pressure has decreased enough, the safety valve will automatically close. Always keep as much distance as possible from venting cylinders. Venting cylinders should never be approached and all gas infrastructure should be checked by a licensed gas fitter.

More information

https://www.elgas.com.au/lpg-gas-bushfire-safety-bush-fire

https://www.elgas.com.au/blog/575-bushfires-bbq-gas-bottles-9kg-45kg

https://www.commerce.wa.gov.au/sites/default/files/atoms/files/lp_gas_cylinder_safety_0.pdf