Divers have a choice of several types decompression table options. Two of these decompression stations are the Hempleman and Air Table. Each table has its own advantages and disadvantages. These tables should be used with care and a diving guide should always be used in conjunction with the decompression table.
Air Table decompression tables
Decompression tables were developed in the 1930's by the Navy's Naval Experimental Diving Unit. They created the first standardised tables based upon a theory. The theory suggested that nitrogen can be eliminated in a linear fashion by the human body, and not at an exponential rate. To accommodate this theory, decompression tables have been created to help divers stay safe and sound underwater.
Originally, diving practitioners relied on 'per compartment' accounting, which is a more conservative approach to determining nitrogen content. This method compares the various compartment gases to a matrix called M-values. These values are often referred to as 'half times' by diving professionals. However, they can only be mathematical expressions, and not real entities. This method is conservative in the short-term and may not be correct for deep, long dives.
Hempleman's despression tables
Val Hempleman's decompression tables helped the Royal Navy stay on the cutting edge of deep diving technology and saved many lives. Hempleman's tenure as the Royal Naval Physiological Laboratory Superintendent from 1968 to82 saw him work 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. Although he was initially unsuccessful in getting the Navy to adopt his new tables, he made modifications based upon his diving experience. The updated tables were finally adopted by the Navy in 1972.
Hempleman's revised despression tables
Hempleman revised the decompression tables for diving in 1968. These tables have a variable ratio between tissue nitrogen tension and 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.
In 1908, Haldane's first table model was published. Haldane, an avid self-experimenter, published the first officially recognized diving tables in 1908. His experimental studies included animal experiments and the first decompression table for the British Admiralty. As a clinical endpoint to decompression sickness, Haldane's suggestions were extensively used.
Hempleman's modified Decompression Tables
Hempleman revised decompression charts in 1968 to incorporate a variable ratio for tissue nitrogen tension and ambient press. However, the Navy rejected the changes and refused permission to implement them. Hempleman was able to modify the tables for practical reasons. Later, these tables were reproduced in metric units. They were adopted by U.S. Navy 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.