Divers can choose from several different types of decompression plates. The Air Table and Hempleman's decompression tables are two such decompression tables. Both tables have their advantages and disadvantages. These tables should not be used without care.
Air Table decompression tables
The first decompression tables were created by the Navy's Naval Experimental Diving Unit in 1930. It was based on an original 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 method compares the various compartment gases to a matrix called M-values. Diving practitioners often refer to these values as 'half-times', though it is important to note that they are only mathematical expressions, not real entities. 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 tables saved many lives and helped the Royal Navy remain at the forefront of deep diving technology. During his tenure as Royal Naval Physiological Laboratory superintendent from 1968 to 1982, Hempleman 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.
Hempleman revised his tables in 1968. He added a variable rate of tissue tension to ambient pressure. He was initially unable get the Navy adopt the new tables but modified them based his diving experience. The Navy adopted the updated tables in 1972.
Hempleman's revised decompression tables
Hempleman published revised diving decompression tables in 1968. These tables include a variable ratio of tissue nitrogen tension to ambient 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.
The first table based on Haldane's model was published in 1908. In 1908, Haldane published the first known diving tables. He was an adventurous self-experimenter. His experiments included animal experiments as well as the creation of the first British Admiralty decompression table. The clinical endpoint of decompression sickness was widely used by Haldane.
Hempleman's modified compression tables
In 1968, Hempleman revised the decompression tables to include a variable ratio of tissue nitrogen tension to ambient pressure. However, the Navy did not approve of the changes and refused to implement the tables. Hempleman decided to alter the tables for practical purposes. These tables were later reprinted using metric units, and adopted by U.S. Navy in 1972.
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 also began using the C and R tables in the same decade. This practice was popularized in the 1980s.