You ever seen the video of the not-so-bright kid that sets a pumpkin full of gas on fire, then punts it with a golf club?
The surface of the fuel burns nice and calm sitting there. This is because only the vapor and the fuel immediately in contact with air is burning. When the putz smacks it and the fuel turns more into vapor and mixes with the air, it sets him ablaze in a massive fireball.
Vapor is MUCH more explosive and a fire hazard than a pool of gas.