I don't really get those who just go ahead and run without an air filter. There's more crap in the air than people think. Pantyhose don't work all that well, the layers move too much and allow grit to vibrate through. Go on treatland, get the little black cap and mesh filter, buy some air filter foam (Treats has it for $1 in a 4x4 square. Amazon and most hardware stores would have something that'd work), rip out all but one of the screen layers and replace that with a circle of foam.