Creating dusty atmosphere

1. CHOOSING THE RIGHT IMAGE
Start by opening an image of an image on which you want to create dusty effect preferably an image with ground area.
2. REMOVING SHARPNESS

Duplicate layer. From "Filter" menu select "Blur>>Gaussian Blur ". Apply settings as shown.

Change the layer mode to "Screen".

3. CREATING DUST
Press Q to enable quick mask. From "Filter" menu select "Render>>Difference Clouds". Apply settings as shown.
Press Q again to disable quick mask. Create a new layer and fill with dust color.
Change the layer mode to "Darken".

4. APPLYING FINAL TOUCHES
Duplicate the layer and scale down horizontally.
Click add layer mask button from the bottom of the layer palette. Apply a black to white gradient to create a smooth blend.