Related Clues:

• Hazy layer
• Stainer of Santa's coat
• Component of Japanese sumi ink
• Pollution portmanteau
• Burnt-coal residue
• Target of a sweep
• Dirty air
• Clean air hurdle
• Possible cause of heavy breathing
• Visibility obstacle
• It's black in a stack
• Chimney stuff
• City haze
• L.A.'s haze
• Sight inhibitor, often