Virginia

Smells like overcooked cabbage to me.

Anyhow, I hope the driver survived - and gives up smoking.

I guess - third degree burns, blown eardrums, major hair loss at a minimum?
(Missed any reference to injuries.)

In it's defence, a propane + air explosion is quite gentle, unlike dynamite.
Relatively slow fire front wave progression, brief exposure to high flame front temperature.
Damage is done by the pressure build up.

Yes, I experimented in my youth.

Balloon with propane/air mix, string attached, light the string, let the balloon go.
And watch the fireball.

Not recommended, but yeah, I was a teenager . . .