REPEX habitat diving procedures: Repetitive vertical excursions, oxygen limits, and surfacing techniques. Technical Report 88-1B.

Abstract

These procedures~designated "Repex"--are designed for divers, diver- scientists particularly, working out of seafloor habitats. They cover habitat depths from 30 to 120 fsw (feet of sea water), with the habitat filled with a nitrogen-oxygen mixture (nitrox) at a PO2 of 0.3 to 0.35 atm. The establ i shed "NOAA OPS" procedures for performi ng descend ing excurs i ons with divers breathing air have been improved. Longer times and repetitive excursions are allowed, but some specific excursions are shorter. Excursions cover the range 65 to 240 fsw* but with only short excursions deeper than 200 fsw. Repetitive dive intervals range between 1/2 and 16 hours; a new sequence starts after 16 hours. The number of the repetitive dive in a sequence and the interval since the last dive determine the repetitive excursion time. Provision is also made to adjust for an excursion following one that uses less than its maximum allowable time. 'One-stop" dives with a primary decompression stop 15*5 fsw deeper than the habitat provide for longer excursion times; these require a 2-min preliminary stop. A new approach is taken toward oxygen exposure limits. Prevailing USN/NOAA rules to prevent CNS toxicity are used deeper than 200 fsw; shallower than this the 1 imits are based on pulmonary and chronic 02 toxicity. These allow a daily dose (using the CPTD method of counting the dose) that varies with overall mission duration, and they are just as safe and much less restrictive than earlier rules. Procedures for ascent from saturation require slower ascent rates for deeper dives, and may start at a depth deeper than storage to account for excursions in the last 36 hours. A representative decompression time--after excursions from saturation at 80 fsw is just over 51 hours. Several plans for surfacing are given, for the different types of equipment that might be used, and for emergencies. Procedures provided for treatment of decompression sickness in habitat diving are based on accepted practices and consider the operational limitations.[Procedures report to Office of Undersea Research, NOAA, U.S. Dept. of Commerce, under contract NA-84-DGC-00152. Tarrytown, NY: Hamilton Research Ltd., 30 Sep 1987.]