Chapter 16 

 SEALAB II ATMOSPHERE CONTROL 



W. F. Mazzone 

 Submarine Medical Center 

 New London, Connecticut 



INTRODUCTION 



Sealab II was initially charged with a mixture of compressed air and helium, producing an 

 atmosphere which contained 4.5 percent oxygen, 17.4 percent nitrogen, and the balance (78.1 

 percent) helium. With relatively small changes, this basic atmosphere was maintained through- 

 out the entire operation. 



Pressure within the habitat, as read out on the gage in the atmosphere control van, averaged 

 100.7 pounds per square inch absolute (psia), equivalent to a gage depth of 193 ft. Variations 

 with the tide were from 191 to 196 ft gage. 



ATMOSPHERE ANALYSIS 



During the entire period in which Sealab II was occupied by personnel, frequent monitoring 

 of the habitat atmosphere was carried out in the atmosphere-control van of the support vessel, 

 Berkone. A sampling line incorporated in the umbilical to the habitat permitted direct sampling 

 of the Sealab atmosphere at any time. The analysis was performed by gas-absorption chroma- 

 tography, using a modified Fisher -Hamilton gas partitioner. This method gave good results for 

 oxygen, nitrogen, and carbon dioxide, but would not measure helium directly, since helium was 

 used as the carrier gas. Helium concentration was estimated by subtracting the total of the 

 three measured gases from 100 percent. Commercially prepared standards of oxygen, nitrogen, 

 and carbon dioxide in helium (all in approximately the concentrations being measured in the 

 Sealab atmosphere) were used to calibrate the partitioner. 



Analysis for trace quantities of hydrocarbons in the habitat atmosphere were carried out 

 by Doctor Merle Umstead of the Naval Research Laboratory, using a gas-liquid chromatographic 

 method. Samples for these analyses were obtained by opening evacuated steel bottles in Sealab 

 II, then reseating them and sending them to the surface. This method prevented hydrocarbon 

 contamination of the samples, which would have resulted from passing them through the rubber 

 sampling hose. Many chromatographic peaks were found, indicating the presence of minute 

 quantities of many different organic compounds. Full identification of these compounds is as 

 yet incomplete. 



Some of these steel flasks were returned to Doctor Ray Saunders at the Naval Research 

 Laboratory for further analysis. Precise carbon monoxide measurements have been requested 

 on these samples. 



Semiquantitative analyses were made for carbon monoxide both topside and in Sealab, using 

 portable tube-type detectors (Draeger, MSA, and Kitagawa). These analyses yielded no positive 

 results, except in the case of carbon monoxide. On several occasions, carbon monoxide levels 

 in the range of 20 to 30 parts per million were indicated by the tubes. These techniques are 

 rather inaccurate at low concentrations. One sample was analyzed by the Linde Corporation, 

 with results on two determinations of 20 and 20.5 parts per million. It is hoped that other 

 accurate carbon monoxide measurements can be made on some of the samples returned to NRL. 



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