Various types of decompression tables are available for divers. Two of these decompression stations are the Hempleman and Air Table. Both tables have both their benefits and drawbacks. These tables should be handled with care. Always use a dive guide in conjunction with the decompression Table.
Air Table decompression tables
The development of decompression tables dates back to the 1930's when the Navy's Naval Experimental Diving Unit developed the first standardized tables based on a theory. This theory stated that the human body is able to eliminate nitrogen in a linear fashion, rather than at an exponential rate. This theory was reflected in decompression tables, which were designed to aid divers staying safe underwater.
Originally, diving practitioners relied on 'per compartment' accounting, which is a more conservative approach to determining nitrogen content. This method uses the M-values matrix to compare the various compartment gases. These values are often referred to as 'half times' by diving professionals. However, they can only be mathematical expressions, and not real entities. Air tables that are based on this method tend not to be accurate for long, shallow dives.
Hempleman's despression tables
Val Hempleman's deep diving tables saved many lives and helped the Royal Navy remain at the forefront of deep diving technology. During his tenure as Royal Naval Physiological Laboratory superintendent from 1968 to 1982, Hempleman worked to overcome "the bends." His research on decompression table helped a man survive ten hours at the depth of 1,535 feet.
Hempleman changed his tables to include a variable ratio for tissue nitrogen tension and ambient press in 1968. He was initially unable to get the Navy to adopt the new tables, but made modifications based on his practical diving experience. The Navy finally adopted the revised tables in 1972.
Hempleman's revised table of decompression
Hempleman's 1968 revised decompression table for diving was published. These tables provide a variable ratio in tissue nitrogen tension to ambientpressure. Although initially the Navy didn't like the results, Hempleman modified these tables for practical purposes. In 1972, the Navy adopted the new tables.
In 1908, Haldane's first table model was published. Haldane, an avid self-experimenter, published the first officially recognized diving tables in 1908. His experiments included animal research and the development of the first British Admiralty-approved decompression table. Haldane’s clinical guidelines were widely adopted as a guideline for decompression sick.
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. The Navy was not happy with the proposed changes and refused to allow them to be implemented. Hempleman decided to alter the tables for practical purposes. These tables were later reproduced in metric units and were adopted by the U.S. Navy in 1972.
The tables were adopted by the British Royal Navy in 1908 and they were used until the 1950s when they were redesigned due to concern that they were too conservative. In the same decade, U.S. Navy adopted what are now called C- and R tables. This practice became widespread in the 1980s.