temperature at the dive location varies 

 widely about the 65"F value. The last am- 

 bient temperature measurement taken by 

 the vehicle's occupants (38 minutes prior to 

 entanglement) showed 51.8 °F, and the com- 

 munications log showed 45°F temperature 

 within the aluminum lock-out cylinder some 

 8 hours later. At this unexpected tempera- 

 ture the Baralyme's effectiveness was se- 

 verely curtailed. Indeed, no indication of 

 such low water temperatures was indicated 

 even from historical data. Another consider- 

 ation became evident in the characteristics 

 of the different pressure hull materials used 

 for the aluminum lock-out chamber and the 

 forward acrylic sphere. Unlike aluminum, 

 acrylic plastic has a low heat transfer coeffi- 

 cient and the operation of equipment therein 

 maintained a temperature of 70 °F at which 

 the Baralyme functioned adequately. At the 

 very least, the JOHNSON SEA LINK tragedy 

 demonstrated how paltry our knowledge of 

 the ocean is. While there is much we can 

 predict about it generally, there are few 

 areas that we can predict specifically, and it 

 is within this broad host of unknowns that 

 the submersible dives. 



Trace Conlaniinants: 



The broad spectrum of trace contaminants 

 generally includes all atmospheric contami- 

 nants, other than carbon dioxide, produced 

 by the human occupants, the electronic or 

 mechanical machinery, paints and solvents 

 and, in some vehicles, batteries within the 

 pressure hull. Referring back to Table 9.2, it 

 is obvious that a wide variety of such con- 

 taminants can evolve. The critical factor in 

 this category is time of exposure, and most 

 vehicles do not have a submerged endurance 

 which allows these contaminants to reach 

 toxic levels. This is not to imply that the 

 evolution of trace contaminants may be ig- 

 nored, but their detection and removal have 

 been a secondary consideration by most de- 

 signers because of the short diving time. 

 But, as the JOHNSON SEA LINK and the 

 PISCES III incidents demonstrated, life sup- 

 port for routine diving is not a difficult prop- 

 osition; it is the non-routine dive that intro- 

 duces the moment of truth. 



The ABS has divided trace contaminants 

 into "unavoidable" and "avoidable" — the for- 

 mer being those produced by the human 

 body in its normal functions (e.g., Hj, COj, 

 NH3, HjS, SO2, CH4 and forms of aldehydes 

 and alcohols) and the latter being those pro- 

 duced by equipment for cooking. Under 

 avoidable contaminants they caution that all 

 instruments should be carefully selected to 

 avoid contaminant production. Mercury 

 thermometers should be avoided and non- 

 reactive protecting and insulating electronic 

 materials should be used. 



Both the ABS and the U.S. Navy require 

 that a sample of cabin air, obtained under 

 simulated closed hatch operations, be ana- 

 lyzed by chromatography. Such analyses 

 must be performed for initial certification/ 

 classification, and thereafter when major 

 overhauls are conducted. The Navy further 

 requires these analyses whenever the inte- 

 rior is repainted or cleaned with solvents 

 that contain hydrocarbons or other toxi- 

 cants. 



Removal of trace contaminants can be per- 

 formed by absorption, adsorption or oxida- 

 tion, and the following compounds may be 

 used either actively (by incorporating them 

 in the scrubber system) or passively (by plac- 

 ing them in panels or devices into which 

 cabin air can circulate under natural convec- 

 tion currents or circulating fans): Activated 

 charcoals, LiOH, soda lime or other alkaline 

 earths and Purafil (activated alumina im- 

 pregnated with potassium permanganate). 

 In the few submersibles that take specific 

 measures to remove trace contaminants, ac- 

 tivated charcoal or carbon is preferred. la- 

 nuzzi (10), in discussing the role of activated 

 charcoal in odor removal, relates that the 

 occupants of DS-4000 reported no discom- 

 forting effects from the cabin aroma whether 

 charcoal was used or not used; consequently, 

 its addition to the LiOH cannister was dis- 

 continued. 



In those submersibles where the batteries 

 are stored in the pressure hull, the role of 

 Hydrocaps in recombining the hydrogen gen- 

 erated with oxygen into water was discussed 

 in Chapter 7. It will suffice to mention that a 

 number of submersibles with in-hull battery 

 arrangements also include hydrogen detec- 

 tors to monitor cabin air. 



426 



