Why does 'smoke' rhyme with 'choke'?

Every morning on my way to work I pass the smokey chimneys of the local GIB factory. I don't even know what it is they spew into the air... poisonous stuff, lethal fumes or simply some steam. The fact that the factory is situated in a residential area hopefully means it's nothing too serious.

Anyway, today was a fine crispy winter morning, clear blue sky, bright sun and the perfect angle; who would have thought that factory smoke could look this good?

Also another back blip... just one this time... HERE.