pretty much none, unless you stop in one place, you have to focus on what your commanding or else it doesn't ahve an affect....although he can order the air to "Solidify" at a higher level and stop you flat, although at the starter power you can only command objects to do something that they can do naturally......such as age, or burn, or float, or crumble, etc.
Welcome one and All to the Jesters Carnival, where the prizes are greater than your wildest dreams, but the nightmares here shall silence you before you can even scream.