Question

why are petrol tanker cansidered even more dangerous when they have just been emptied than when they are full

Answer 1

this is because when the tanker is full with petrol their is no presence of oxygen in it...and f there will be no oxygen then it will not get lighted...another reason is that petrol first is converted into vapours when it is kept open and the vapours burn actually..and if there is no place for vapours of petrol in tank then there is very less chance getting lighted... but when the tank is empty the little bit petrol left into the tank changes into vapours and spreads all over the tank and even then the oxygen is also present... and if the vapours get lighted by heat or anything then....it will go... BOOM BOOM... and you'll watch the light show....