Most of the Engineers already know that you will need a lot of Volatile Air to make Electrified Ether (http://cata.wowhead.com/item=67749#reagent-for), and You need Electrified Ether for a lot of the new Engineering recipes.
There are no gas clouds anymore for engineers, instead there is a new device called Electrostatic Condenser (http://cata.wowhead.com/item=67494) and here is the description: "Allows a skilled engineer to occasionally collect Volatile Air while mining, skinning, or collecting herbs."
I first tried to farm Volatile Air by killing mobs with a lvl 85 warrior in full heroic blue gear. I got 3 Volatile Air after farming for 17 minutes. I used around 60 just to reach 525 in engineering so it's a really low drop rate I would say, and there is only one place where you can farm it in Twilight Highlands. (at least I couldn't find other places)
Today, I leveled mining with my engineering character and I was suprised how often Volatile Air drops, in about 4 minutes I mined 12 Obsidium Deposit, and I found Volatile Air in 9 of them, 3 out of these 9 gave me 2 Volatile Air, so I got 12 Volatile Air in about 4 minutes.
UPDATE:
I just finished leveling mining.
Number of items I got between 425-525:
28 Volatile Earth
25 Volatile Water
23 Volatile Fire
139 Volatile Air
I think they will nerf the droprate, it just seems too high compared to the others.
original post: http://www.wow-professions.com/news/...ring-cataclysm