The oil from Tengiz field comes out of the wells hot and at a very high pressure, believed to be the highest in the world. It also contains large proportion of gas which is rich in the compound hydrogen sulfide yielding poisonous sulfur. A 1985 explosion in which one man was killed caused a -high column of fire visible from . The deadly gas made it impossible for Soviet firefighters to quickly extinguish the fire. The well burned for a period of one year and was finally capped