Hi,
I have been trying both quests with Gas Bag, from the Abomination Factory. When accepting quests for the different constructs, you get an item for each called Call [Construct Name]. The item Call Gas Bag does not allow the player to summon Gas Bag. I seen other players report the same issue on wowhead. The item does not work for the quest Herbicidal Tendencies or Special Formula.
There is no other constructs active at the time of using the item. Workaround currently is to fetch Gas Bag at the Abomination Factory before attempting to complete the quest.