Divers have many options for decompression tables. Two of these decompression stations are the Hempleman and Air Table. Both tables have their own benefits and drawbacks. These tables should not be used without care.
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. The theory suggested that nitrogen can be eliminated in a linear fashion by the human body, and not at an exponential rate. As a result, decompression tables were developed to accommodate this theory and help divers stay safe 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 sometimes called "half-times" by diving practitioners. However, it is important that these numbers are not real entities and only mathematical expressions. Air tables that are based on this method tend not to be accurate for long, shallow dives.
Hempleman’s decompression tables
Val Hempleman’s deep diving technology was saved by the Royal Navy's use of decompression tables. Hempleman was the Royal Naval Physiological Laboratory's superintendent between 1968 and 1982. He worked tirelessly 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 to get the Navy to adopt the new tables, but made modifications based on his practical diving experience. In 1972, the Navy adopted the updated tables.
Hempleman's revised Decompression Tables
Hempleman published revised diving decompression tables in 1968. These tables show a variable ratio for tissue nitrogen tension to ambient air pressure. 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 was an ambitious self-experimenter who published the first recognised 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 depression tables
Hempleman modified the decompression tables in 1968 to include a variable proportion of tissue nitrogen tension to ambient. However, the Navy refused to approve the changes and refused the tables' implementation. Hempleman had to amend the tables for practical use. 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.