Divers have many options for decompression tables. These decompression tables include the Air Table, and Hempleman’s. Each table has its advantages and drawbacks. These tables should not be used without care.
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. This theory stated that the human body is able to eliminate nitrogen in a linear fashion, rather than at an exponential rate. As a result, decompression tables were developed to accommodate this theory and help divers stay safe underwater.
Initial diving practices used 'per compartment accounting' to determine nitrogen content. This was a conservative approach. This method compares each compartment gas to a matrix called the 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 decompression tables helped the Royal Navy stay on the cutting edge of deep diving technology and saved many lives. Hempleman, who was Royal Naval Physiological Laboratory chief from 1968 to 1982 worked to overcome the "bends." His research on the decompression tables was instrumental in helping a man survive for ten consecutive hours at a depth of 1.535 feet.
In 1968, Hempleman revised his tables and included a variable ratio of tissue nitrogen tension to ambient pressure. After initially being unable to convince the Navy to adopt the tables, Hempleman made modifications based in his diving experiences. The Navy finally adopted the revised tables in 1972.
Hempleman's revised decompression tables
Hempleman revised the decompression tables for diving in 1968. These tables provide a variable ratio in tissue nitrogen tension to ambientpressure. 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 published the first table that was based on his model. 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 compression 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 had to amend the tables for practical use. In 1972, the U.S. Navy adopted these tables in metric units.
The British Royal Navy adopted the tables back in 1908 and used them until 1950s. The U.S. Navy also began using the C and R tables in the same decade. This practice was popularized in the 1980s.