Maya - Lighting and Rendering 2 - Fog (Legacy) and Atmosphere

 In the Arnold render setting there is an option to create aifog. This creates a fog like texture  which can be placed around the scene with settings to create the desired effect as well as changing colour. By adding a temporary background in the render view you can create some interesting effects. 

Arnold also offers aiatmosphere volume. This creates a similar fog like effect to make the atmosphere in your scene more of less dense. Like many other lighting or rendering options as soon as you add these to a scene it slows down render times, however it works effectively to create atmosphere in a scene.