The volumetric particles Are more of a rough idea of the density in the air in that general area. It renders all the particles to a bunch of slices that are distributed along the cameras view. Lowering the particle Density Distance will give more detail with in that area. If you still cant get the quality you want for the density particles, You can increase the number of slices it renders out at the cost of some performance. There is an objects called HXUsedShaders that has a setting called Density Particle Quality. Increase that and hit build shaders to apply those settings. This quality setting cant be changed at runtime. If you need tighter control over what areas are dusty, Use a density area script. Although you can only have a small number of those.