(1)Gas cloud will formed near leak source after toluene leakage and then the toluene volatile upward. When the toluene
vapor reaches certain height, the vapor will deposit under the action of gravity and then it will diffuse from the center to the surroundings.
(2)In the lower plane from evaporation source, at the beginning, the concentration of the center is larger, but as time goes
on, the concentration in the center decreases and finally is lower than in the surroundings.
(3)During the toluene evaporation, the concentration near corners has been very low which explaining that the concentration close to obstacles is low. So closing obstacles in toluene leakage is relatively safe.
(4) The concentration of each position in space increases with time but the increasing rate is non-constant. So toluene
vapor accumulates layer by layer during the diffusion.