Purity of acetone is important. Actually, what is more important is what the acetone leaves behind after it evaporates. Any time you buy acetone, it is important to pour an ounce or so into a glass container, and leave it to evaporate. There should be no residue that does not evaporate, otherwise this is an unknown and potentially toxic contaminant that will likely be left in the final product. Since substances are usually separated from acetone by evaporation, any toxic contaminants will be super-concentrated when they remain.
Acetone is extremely flammable. Its vapors are heavier than air, and can travel many meters across floors and down stairs. If it reaches a spark or a pilot light, a dangerous explosion will result. Fans can be used to accelerate the evaporation of acetone, but they must contain brushless motors. (Non-brushless motors generate internal sparks during normal operation, which will also ignite acetone vapors).
Acetone will dissolve many plastics. Even just the vapors can do serious damage to plastics. Keep acetone away from sensitive plastic items such as CD's, computer monitors, electronics, etc. and remember that acetone vapor can travel across a table or a desk and damage other plastic items sitting on it. Do not use unsafe plastic containers to hold acetone, as the acetone will eat right through them.
One particular plastic known to be safe for use with acetone is polypropylene. Polypropylene is used to make many containers, such as drink cups and pharmacy pill bottles. Polypropylene containers can be identified by a recycling symbol with the number 5 inside and the letters PP below.