Divers have many options for decompression tables. The Air Table and Hempleman's decompression tables are two such decompression tables. 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. The theory suggested that nitrogen can be eliminated in a linear fashion by the human body, and not at an exponential rate. Therefore, decompression plates were created to accommodate this theory. They also help divers remain safe underwater.
Divers used to use 'per container' accounting in the beginning. This is a more conservative way of determining nitrogen content. This method compares each compartment gas to a matrix called the M-values. 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. These air tables are conservative for short-term dives and can be inaccurate for shallower, longer dives.
Hempleman's Decompression Tables
Val Hempleman’s decompression tables were a lifesaver for many people. Hempleman, who was Royal Naval Physiological Laboratory chief from 1968 to 1982 worked to overcome the "bends." His research on decompression tables helped a man survive for ten hours at a depth equivalent to 1,535 feet.
Hempleman modified his tables and added a variable proportion of tissue nitrogen tension to ambient. This was done in 1968. The Navy was initially resistant to Hempleman's changes, but he modified them based on his diving experience. The Navy finally adopted the revised tables in 1972.
Hempleman's revised despression tables
In 1968, Hempleman published revised decompression tables for diving. These tables provide a variable ratio in tissue nitrogen tension to ambientpressure. These results were not appreciated by the Navy at first. Hempleman made modifications to the tables for practical reasons and the Navy adopted the new tables in 1972.
In 1908, Haldane published the first table that was based on his model. Haldane was an ambitious self-experimenter who published the first recognised diving tables in 1908. His experiments also included animal studies and the design of the British Admiralty's first decompression tables. As a clinical endpoint to decompression sickness, Haldane's suggestions were extensively used.
Hempleman's modified compression tables
Hempleman modified the decompression tables in 1968 to include a variable proportion of tissue nitrogen tension to ambient. However, the Navy did not approve of the changes and refused to implement the tables. Hempleman decided to alter the tables for practical purposes. Later, these tables were reproduced in metric units. They were adopted by U.S. Navy 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. In the same decade, U.S. Navy adopted what are now called C- and R tables. This practice became widespread in the 1980s.