Divers can choose from several different types of decompression plates. These decompression tables include the Air Table, and Hempleman’s. Both tables have their 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 have been developed since the 1930s, when the Navy's Naval Experimental Diving Unit first created standardized tables that were based on 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.
Divers used to use 'per container' accounting in the beginning. This is a more conservative way of determining nitrogen content. This compares the different compartment gases to an M-values matrix. 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. During his tenure as Royal Naval Physiological Laboratory superintendent from 1968 to 1982, Hempleman worked 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 updated his tables in 1968 and added a variable ratio between tissue nitrogen tension and ambient pressure. The Navy was initially resistant to Hempleman's changes, but he modified them based on his diving experience. The updated tables were finally adopted by the Navy in 1972.
Hempleman's revised tables of decompression
Hempleman revised the decompression tables for diving in 1968. These tables include a variable ratio of tissue nitrogen tension to ambient pressure. These tables were not initially liked by the Navy. Hempleman changed the tables to make them more practical and the Navy adopted them 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 work included animal experiments and the publication of the first British Admiralty dive table. The clinical endpoint of decompression sickness was widely used by Haldane.
Hempleman's modified Decompression Tables
Hempleman revised decompression charts in 1968 to incorporate a variable ratio for tissue nitrogen tension and ambient press. The Navy was not happy with the proposed changes and refused to allow them to be implemented. Hempleman had to amend the tables for practical use. 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. In the same decade, the U.S. Navy began using what are now known as C and R tables, and this practice became common in the 1980s.