Development and Evaluation of Hyperbaric Carbon Dioxide Analyzer for Dry Deck Shelter Operations

Abstract

The Dry Deck Shelter (DDS) is a hyperbaric system used on submarines to transport SEAL delivery vehicles into an operating area. The system uses air from submarine banks to ventilate the DDS and provide breathing air to the divers. Because of the lack of carbon dioxide (CO2) monitors, ventilation schedules are currently based on predictions to avoid exceeding the within-DDS CO2 limit of 1.5percent (15,000 ppm) surface equivalent (sev). To improve efficiency of DDS ventilation, we proposed using portable CO2 analyzers that are adapted for use in the DDS. An off-the-shelf non-hyperbaric analyzer was extensively modified to read up to 2.5percent (25,000 ppm) CO2 sev at pressures up to 6 atmospheres absolute (ATA). Experiments evaluating instrument performance and the effects of humidity and ambient temperature in the laboratory demonstrated accuracy of +/- 10percent relative over 1-6 ATA. Field testing during DDS operations demonstrated the analyzer worked reliably and agreed closely with subsequent laboratory analysis of air samples. Results indicated current ventilation procedures often produced CO2 levels substantially lower or higher than the current limit. In addition to meeting the requirements for CO2 measurement during DDS operations, this analyzer may also fill the existing need for reliable CO2 measurement inside other types of hyperbaric chambers and diving apparatus.