Syndrome symptoms. 1983: Cave diver Jochen Hasenmayer uses heliox to a depth of 212 meters. Depth is later repeated by Sheck Exley in 1987. 1987: First mass use of trimix and heliox: Wakulla Springs Project. Exley teaches non-commercial divers in relation to trimix usage in cave diving. 1991: Billy Deans commences teaching of trimix diving for recreational diving. Tom Mount develops first trimix training standards (IANTD). Use of trimix spreads rapidly to North East American wreck diving community. 1992: The National Oceanographic and Atmospheric Administration (NOAA) develops "Monitor Mix" for dives to the USS Monitor. This mix became NOAA Trimix I, with decompression tables designed by Bill Hamilton published in the NOAA Diving Manual. 1992: NOAA obtains training from Key West Divers to conduct the first NOAA-sponsored trimix dives on the wreck of the USS Monitor off Cape Hatteras, NC. 1994: Combined UK/USA team, including wreck divers John Chatterton and Gary Gentile, successfully completes a series of wreck dives on the RMS Lusitania expedition to a depth of 100 meters using trimix. 1994: Sheck Exley and Jim Bowden use "heliair" at Zacaton in the first attempt to make an open circuit scuba dive to 1000 ft. Exley, at the time holding the world record for an 881-foot dive, passes out and dies around 900 feet; Bowden aborts at 925 feet and survives despite several life-threatening obstacles. 2001: The Guinness Book of records recognises John Bennett as the first scuba diver to dive to , using trimix. 2005: David Shaw sets depth record for using a trimix rebreather, and dies while repeating the dive to attempt to recover the body of another diver. 2015: The United States Navy Experimental Diving Unit shows that bounce dives using trimix are not more decompression efficient than dives on heliox. Training and certification Technical diver training and certification agencies may differentiate between levels of trimix diving qualifications, The usual distinction is between normoxic trimix and hypoxic trimix, sometimes also called full trimix. The basic distinction is that for hypoxic trimix diving the dive cannot be started on the bottom mix, and procedures for use of a travel mix for the first part of the descent, and gas switching during the descent to avoid oxygen toxicity are added to the required skills. Longer decompression using a larger variety of mixtures may also complicate procedures. In closed circuit rebreather diving, use of a hypoxic diluent prevents the