This was a tragedy occured on Dec 4th 1952.A sudden change in climate occured due to an air current tn Themes river valley in London.A heavy current of moderate hot air occured over the cold air.As a result after sunset fog begane to spread over London and temperature fell down.
Poeple were unable to withstand the sudden cold climate.As a usual practice they begane to light up their heaters.The fuel of most of the heaters were coal.As a result dense black smoke begane to rise to atmosphere from thousands of houses.
On next day this smoke , sulphur dioxide , smoke from different factories and various chemical wastes begane to concentrate in atmosphere over London.This dense cover of air prevented sunlight reaching the ground.As a result temperature begane to fall below normal.People begane to shiver in freezing cold and the heaters produced insufficient heat. In blood freezing cold hundreds of poeple died and many got hospitalised.
What actually happened was , when people burned coal first carbon dioxide released.Due to insufficient air circulation carbon monoxide also formed.The sulphur in coal joined with oxygen and formed sulphur dioxide .On entering this to the respiratory system it bagane to make problems.sulphur dioxide again reacted with oxygen and formed sulphur trioxide.Sulphur trioxide combined with water to form sulphuric acid.All these chemicals spread over London City as smog.Transport became dead slow causing more pollution.It increased the suffocation to all living beings and subsequent illness , death etc.A similar smog repeated in 1962 and about 700 people lost their life.
Here is a graph showing the death rate of the victims of 1952 London Smog.