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.
He was German, his press was wooden, and the most important aspect of his invention was that it was the first form of printing to use movable type. The earliest dated specimens of printing by Gutenberg are papal indulgences (notes given to Christians by the Pope, pardoning their sins) issued in Mainz in 1454.