Divers can choose from several different types of decompression plates. These decompression tables include the Air Table, and Hempleman’s. Both tables have their own 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 first decompression tables were created by the Navy's Naval Experimental Diving Unit in 1930. It was based on an original theory. This theory stated that the human body is able to eliminate nitrogen in a linear fashion, rather than at an exponential rate. Decompression tables were created to support this theory and ensure that divers are safe underwater.
In the beginning, divers used 'per-compartment' accounting to determine nitrogen content. This method uses the M-values matrix to compare the various compartment gases. These values are sometimes called "half-times" by diving practitioners. However, it is important that these numbers are not real entities and only mathematical expressions. The air tables based upon this method are generally conservative and may not work well for long, shallow dives.
Hempleman's Decompression Tables
Val Hempleman's deep diving tables saved many lives and helped the Royal Navy remain at the forefront of deep diving technology. Hempleman's tenure as the Royal Naval Physiological Laboratory Superintendent from 1968 to82 saw him work to overcome "the bends." Hempleman's research into decompression tables enabled a man to survive for ten hour at a depth equivalent 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 updated tables were finally adopted by the Navy in 1972.
Hempleman's revised table of decompression
Hempleman revised the decompression tables for diving in 1968. These tables allow for a variable ratio of tissue tension to ambient 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.
The first table based on Haldane's model was published in 1908. Haldane was an independent experimenter who published the first diving tables in 1908. His experiments also included animal studies and the design of the British Admiralty's first decompression tables. Haldane's recommendations were widely used as a clinical endpoint for decompression sickness.
Hempleman's modified depression tables
Hempleman modified the decompression tables in 1968 to include a variable proportion of tissue nitrogen tension to ambient. The Navy opposed the changes and refused implementation of the tables. Hempleman changed the tables to make them more practical. Later, these tables were reproduced in metric units. They were adopted by U.S. Navy 1972.
The British Royal Navy adopted the tables in 1908 and continued using them until the 1950s, when they were revised because of concerns that they were too conservative. The U.S. Navy started using what is now called C and R table in the same decade. This practice became more common in 1980s.