First, the extinguisher valve is removed and the threads and interior of the cylinder are checked for corrosion, pitting, and any other abnormalities. [29 CFR 1910.157(f)(3)] If the cylinder passes the visual inspection, it is placed into a steel chamber, which is then filled with water at normal pressure.
Updated April 17, 2017. The earliest dated printed book known is the Diamond Sutra, printed in China in 868 CE. However, it is suspected that book printing may have occurred long before this date. In 1041, movable clay type was first invented in China.
In the mid-15th century Johannes Gutenberg invented a mechanical way of making books. This was the first example of mass book production. Before the invention of printing, multiple copies of a manuscript had to be made by hand, a laborious task that could take many years. Later books were produced by and for the Church using the process of wood engraving.