what's the difference: bubbler vs flashback arrestor?

[needanswer]

more newbie questions.

is the only difference that bubbler uses a liquid
and flashback arrestor is a porous solid?

I think both serve the purpose of preventing flame from going back in the generator. Also, they have the side effect of trapping some of the electrolyte in the form of vapor.
Do they serve any additional purpose?

is it necessary to have a bubbler or flashback arrestor if my generator has a pop cork/cap ? (i.e. if pressure inside is great, a cap would pop to prevent the whole container from breaking). also, the gas is going to the car's air filter box. I'm not sure where a flame would come from.

thanks

[Bob Boyce]