Divers have many options for decompression tables. These decompression tables include the Air Table, and Hempleman’s. Each table has its advantages and drawbacks. These tables need to be used with care. A diving guide should always accompany the decompression table.
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 said that the human body can remove nitrogen in a linear way, not an exponential manner. This theory was reflected in decompression tables, which were designed to aid divers staying safe underwater.
In the beginning, divers used 'per-compartment' accounting to determine nitrogen content. This method compares each compartment gas to a matrix called the M-values. Diving practitioners often refer to these values as 'half-times', though it is important to note that they are only mathematical expressions, not real entities. Hence, the air tables based on this method tend to be conservative in the short term, and may be incorrect for long, shallow dives.
Hempleman’s decompression tables
Val Hempleman’s deep diving technology was saved by the Royal Navy's use of decompression tables. Hempleman, who was Royal Naval Physiological Laboratory chief from 1968 to 1982 worked to overcome the "bends." His research on the decompression tables was instrumental in helping a man survive for ten consecutive hours at a depth of 1.535 feet.
Hempleman revised his tables in 1968. He added a variable rate of tissue tension to ambient pressure. He was initially unable get the Navy adopt the new tables but modified them based his diving experience. The Navy finally adopted the revised tables in 1972.
Hempleman's revised Decompression Tables
Hempleman's 1968 revised decompression table for diving was published. These tables show a variable ratio for tissue nitrogen tension to ambient air pressure. These results were initially not liked by the Navy. However, Hempleman modified them for practical purposes. The Navy adopted the new tables in 1972.
In 1908, Haldane published the first table that was based on his model. Haldane was an intrepid self-experimenter and published the first recognized diving tables in 1908. His experiments included animal research and the development of the first British Admiralty-approved decompression table. Haldane’s recommendations were widely accepted as a clinical indicator for decompression illness.
Hempleman's modified despression tables
Hempleman updated the decompression table to include a variable rate of tissue nitrogen tension relative to ambient pressure in 1968. The Navy was not happy with the proposed changes and refused to allow them to be implemented. This led Hempleman to change the tables for practical purposes. These tables were later reprinted using metric units, and adopted by U.S. Navy in 1972.
The British Royal Navy adopted the tables back in 1908 and used them until 1950s. The U.S. Navy also began using the C and R tables in the same decade. This practice was popularized in the 1980s.