The water gas was a form of fuel gas that was produced by the mixture of coke with high-pressure steam and had two main characteristics: it was odourless and poisonous. Its high risk discouraged Europeans from producing it, whereas on the other side of the Atlantic it grew significantly. The Athens Gasworks started producing water gas at the beginning of the 20th century with a new water gas production unit (Old Watergas). The operation of the unit utilized the coke, which was a by-product of the coal gas production and was piled in large quantities in the yard. After the success of the Old Watergas, a new water gas production unit was added due to the increasing demands (New Watergas).