Divers have many options for decompression tables. Two such tables are the Hempleman's and Air Table decompression table. Each table has its advantages 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. This theory said that the human body can remove nitrogen in a linear way, not an exponential manner. Decompression tables were created to support this theory and ensure that divers are safe underwater.
In the beginning, divers used 'per-compartment' accounting to determine nitrogen content. This compares the different compartment gases to an M-values matrix. These values are commonly referred to by divers as "half-times", but it is important to remember that they are mathematical expressions and not real entities. The air tables based upon this method are generally conservative and may not work well for long, shallow dives.
Hempleman's despression tables
Val Hempleman's decompression table helped save many lives by keeping the Royal Navy at the cutting edge in deep diving technology. Hempleman's tenure as the Royal Naval Physiological Laboratory Superintendent from 1968 to82 saw him work to overcome "the bends." Hempleman's research on decompression tables allowed a man to survive for ten hours at depths equivalent to 1,535 feet.
Hempleman revised his tables in 1968. He added a variable rate of tissue tension to ambient pressure. He was initially unable to get the Navy to adopt the new tables, but made modifications based on his practical diving experience. The Navy finally adopted the revised tables in 1972.
Hempleman's revised despression tables
Hempleman released revised decompression tables in 1968 for diving. These tables show a variable ratio for tissue nitrogen tension to ambient air 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 was an intrepid self-experimenter and published the first recognized diving tables in 1908. His experiments included animal research and the development of the first British Admiralty-approved decompression table. Haldane's recommendations were widely used as a clinical endpoint for decompression sickness.
Hempleman's modified depression tables
Hempleman updated the decompression table to include a variable rate of tissue nitrogen tension relative to ambient pressure in 1968. The Navy opposed the changes and refused implementation of the tables. Hempleman decided to alter the tables for practical purposes. In 1972, the U.S. Navy adopted these tables in metric units.
The British Royal Navy adopted the tables in 1908 and continued using them until the 1950s, when they were revised because of concerns that they were too conservative. The U.S. Navy started using what is now called C and R table in the same decade. This practice became more common in 1980s.