Various types of decompression tables are available for divers. These decompression tables include the Air Table, and Hempleman’s. 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 1930's saw the development of decompression table standards. This was when the Naval Experimental Diving Unit created the first tables that were standardized 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. To accommodate this theory, decompression tables have been created to help divers stay safe and sound underwater.
Initial diving practices used 'per compartment accounting' to determine nitrogen content. This was a conservative approach. This method compares the various compartment gases to a matrix called M-values. 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. 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 table
Val Hempleman’s decompression tables were a lifesaver for many people. 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 modified his tables and added a variable proportion of tissue nitrogen tension to ambient. This was done in 1968. 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 table of decompression
In 1968, Hempleman published revised decompression tables for diving. These tables include a variable ratio of tissue nitrogen 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.
In 1908, Haldane's first table model was published. Haldane was an independent experimenter who published the first diving tables in 1908. His experiments included animal experiments as well as the creation of the first British Admiralty decompression table. Haldane’s recommendations were widely accepted as a clinical indicator for decompression illness.
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 was not happy with the proposed changes and refused to allow them to be implemented. Hempleman changed the tables to make them more practical. In 1972, the U.S. Navy adopted these tables in metric units.
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, the U.S. Navy began using what are now known as C and R tables, and this practice became common in the 1980s.