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.
One of those things you learning in history class that isnât necessarily true: It is a little-known but undisputed historical fact that Johannes Gutenberg did not invent the printing press. Though the Gutenberg Bible was certainly the first mass produced printed work, it was hardly the first printed book â nor was it even the first made using movable type.