Divers can choose from a variety of decompression tables. These decompression tables include the Air Table, and Hempleman’s. Both tables have both their benefits and drawbacks. These tables should not be used without care.
Air Table decompression tables
The first decompression tables were created by the Navy's Naval Experimental Diving Unit in 1930. It was based on an original theory. This theory suggested that the human body could eliminate nitrogen in an exponential fashion. To accommodate this theory, decompression tables have been created to help divers stay safe and sound underwater.
Original diving professionals used "per compartment" accounting as a method to determine nitrogen contents. This compares the different compartment gases to an M-values matrix. These values are commonly referred to by divers as "half-times", but it is important to remember that they are mathematical expressions and not real entities. These air tables are conservative for short-term dives and can be inaccurate for shallower, longer dives.
Hempleman's Decompression Tables
Val Hempleman’s deep diving technology was saved by the Royal Navy's use of decompression tables. Hempleman's tenure as the Royal Naval Physiological Laboratory Superintendent from 1968 to82 saw him work to overcome "the bends." Hempleman's research on decompression tables allowed a man to survive for ten hours at depths equivalent to 1,535 feet.
Hempleman revised his tables in 1968. He added a variable rate of tissue tension to ambient pressure. The Navy was initially resistant to Hempleman's changes, but he modified them based on his diving experience. In 1972, the Navy adopted the updated tables.
Hempleman's revised decompression tables
Hempleman published revised diving decompression tables in 1968. These tables include a variable ratio of tissue nitrogen tension to ambient pressure. Although the Navy initially did not like these results, Hempleman modified the tables for practical purposes and the new tables were eventually adopted by the Navy in 1972.
The 1908 publication of the first Haldane-based table was a result. Haldane was an intrepid self-experimenter and published the first recognized diving tables in 1908. His experiments also included animal studies and the design of the British Admiralty's first decompression tables. The clinical endpoint of decompression sickness was widely used by Haldane.
Hempleman's modified decompression tables
Hempleman updated the decompression table to include a variable rate of tissue nitrogen tension relative to ambient pressure in 1968. However, the Navy did not approve of the changes and refused to implement the tables. Hempleman was able to modify the tables for practical reasons. These tables were later reprinted using metric units, and adopted by U.S. Navy in 1972.
The British Royal Navy adopted them in 1908, and they continued to use them until the 1950s. In the same decade the U.S. Navy used what are now known C andR tables. This practice became popular in the 1980s.