Answer:
An empty fuel tank can still contain "fumes"
Explanation:
Even if there is not enough liquid fuel, whatever is left in the tank creates fumes, which is more combustible than liquid gas.
Answer:
Fumes / vapors.
Explanation:
An empty tank appears to be non dangerous as it has no liquid fuel. However even if tank is empty there may be some drops of left over liquid fuel.
These drops make the container filled with dangerous vapors that are more prone to catch fire as compared to gasoline.
Even a small spark may cause a severe explosion.
