[MichaelCollins]

Mustard isn't like tear gas; it's persistent. It's not really a gas at all; it's actually a mist of liquid droplets. The mist then condenses on everything in the area and contaminates it for weeks. Anybody who comes into contact with it without protective gear (more than a gas mask) will suffer debilitating injuries. If you get it on your skin, your skin will fall off. This makes mustard generally useful for area denial, particularly against opponents that aren't ready to suit up and decontaminate everything. Drop a lot of mustard on a supply depot, command post, etc, and all of that equipment now needs to be decontaminated before it can be used again.