The two first combos are just an example to show the duration of the gas and the damage that can cause. Against some characters you need to walk a little before to connect Gas blast and also there are two types of distances: Walking EX Gas Blast: if you do at perfect distance the gas starts to damage immediately but if the opponent press crouching block the gas cause push back. Neutral Ex Gas Blast: Starts to damage only after to connect an attack/Combo and or if the opponent move forward, jump, or in some cases if attack.