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.
A Buddhist holy text, the Diamond SÅ«tra is considered to be the oldest surviving dated printed book in the world. Found in a walled up cave in China along with other printed materials, the book is made up of Chinese characters printed on a scroll of grey printed paper, wrapped along a wooden pole.