Visibility hindrance is a term used to describe any environmental factor that reduces the visibility of an area. Common examples of visibility hindrances are FOG, SMOG, and HAZE. FOG is a type of visibility hindrance caused by tiny water droplets suspended in the air, which can reduce visibility to a few meters. SMOG is a combination of smoke and FOG, and is usually caused by the burning of fossil fuels. HAZE is a type of visibility hindrance caused by dust, smoke, or other pollutants suspended in the air, which can reduce visibility to several kilometers.