Other examples of the post can be found here, here, here and here on Facebook, as well as on this website. The post ends with an appeal to “save a life today by sharing this information”.
A similar version also appears here on Twitter (screenshot below), although the claim about the dangers of shaking a gas cylinder has been omitted.
NoTICE❗
You don't have to shake the gas cylinder to know the level of it's content.
Just wet a side of the cylinder with water, after a while the used top part will be dry while the lower part with gas will remain wet.
The wet portion tells you the amount of gas left.