Divers can choose from a variety of decompression tables. There are two types of decompression tables: the Air Table and Hempleman's. Both tables have their advantages and disadvantages. These tables should be used with care and a diving guide should always be used in conjunction with the decompression table.
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 suggested that the human body could eliminate nitrogen in an exponential fashion. To accommodate this theory, decompression tables have been created to help divers stay safe and sound 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 commonly referred to by divers as "half-times", but it is important to remember that they are mathematical expressions and not real entities. Air tables that are based on this method tend not to be accurate for long, shallow dives.
Hempleman's decompression table
Val Hempleman’s decompression tables were a lifesaver for many people. Hempleman worked hard to overcome the "bends" during his tenure as Royal Naval Physiological Laboratory supervisor from 1968 through 1982. 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 changed his tables to include a variable ratio for tissue nitrogen tension and ambient press in 1968. After initially being unable to convince the Navy to adopt the tables, Hempleman made modifications based in his diving experiences. The Navy adopted the new tables in 1972.
Hempleman's revised decompression tables
Hempleman revised the decompression tables for diving in 1968. These tables allow for a variable ratio of tissue tension to ambient pressure. These tables were not initially liked by the Navy. Hempleman changed the tables to make them more practical and the Navy adopted them in 1972.
The 1908 publication of the first Haldane-based table was a result. Haldane was an independent experimenter who published the first 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 decompression tables
Hempleman modified the decompression tables in 1968 to include a variable proportion of tissue nitrogen tension to ambient. The Navy was not happy with the proposed changes and refused to allow them to be implemented. Hempleman changed the tables to make them more practical. Later, these tables were reproduced in metric units. They were adopted by U.S. Navy 1972.
The British Royal Navy adopted them in 1908, and they continued to use them until the 1950s. In the same decade, U.S. Navy adopted what are now called C- and R tables. This practice became widespread in the 1980s.