ATMOSPHERE CONTROL HI 



Carbon monoxide was implicated as a possible factor in the headaches which troubled a number 

 of the aquanauts. This points up the importance of providing future Sealab operations with a 

 sensitive, accurate method of measuring carbon monoxide in the habitat atmosphere, in the 

 scuba bottles, and in the compressed air used in charging the personnel-transfer capsule and 

 the deck decompression chamber complex. No such apparatus was present for Sealab II. 



Relative-humidity measurements were made in the habitat, using wet -bulb and dry -bulb 

 thermometers. Special correction factors had to be introduced because of the increased thermal 

 conductivity of the Sealab atmosphere. Relative -humidity values ranged from 60 to 92 percent, 

 staying mostly between 65 to 85 percent. 



Temperature of the habitat atmosphere ranged generally from 80° to 90°F. 



ATMOSPHERE CONTROL 



The principal controlling mechanism used was the Krasberg oxygen sensor and controller, 

 which automatically regulated oxygen levels in the habitat. The Krasberg controller was set 

 for 4.25 percent oxygen (PO 221 mm Hg) during most of the run, with limits of 4.0 percent 

 (208 mm Hg) and 4.5 percent (234 mm Hg). It functioned well and in general maintained atmos- 

 pheric oxygen within prescribed limits. Near the end of the stay of Team 2, oxygen was reduced 

 to approximately 3.5 percent for two days to test the effects of this change on personnel. The 

 lowest level actually recorded was 3.28 percent. 



In the first few days of the run, it was found that the water level in the trunk tended to rise 

 rather rapidly, and had to be blown down with additional gas every few days. After the stopping 

 of some small gas leaks from the habitat, blowdowns were much less frequently required. The 

 blowing was accomplished with either compressed air or helium, depending upon the oxygen 

 level in the habitat at the time. During these early days it was not necessary to bleed any 

 oxygen into the habitat to maintain the desired oxygen tension. This was attributed initially to 

 the compressed air used in blowing down. Later in the stay of Team 1, however, it was dis- 

 covered that compressed air was leaking into the habitat through the pneumatic air hose to the 

 pneumonfathometer. This apparently accounted for the rise in nitrogen during the second week, 

 when it reached a peak of 25.2 percent. 



Carbon dioxide was controlled by means of a specially designed manifold which held twelve 

 standard canisters (6.2 lb) of lithium hydroxide. This scrubber maintained very low levels of 

 carbon dioxide (undetectable to 0.02 percent) for periods of 24 hours or longer. Carbon dioxide 

 would then increase rather rapidly, usually reaching 0.25 percent within about 36 hours after 

 the canisters were changed. At this level (1.7 percent effective at sea level), the aquanauts 

 often were aware of some increase in their rate of breathing and mild discomfort. Canisters 

 were usually changed before carbon dioxide reached 0.3 percent, but on one occasion it rose 

 to 0.42 percent (2.9 percent effective). After canister changes, carbon dioxide concentration 

 fell precipitously, often falling below 0.01 percent in but a few hours. Efficiency of carbon 

 dioxide scrubbing was somewhat diminished late in the run, when some of the lithium hydroxide 

 canisters were replaced with Hopcalite and some with silical gel for humidity control. The 

 principal effects were shortening of canister life by a few hours and raising of minimum carbon 

 dioxide levels from below 0.01 percent up to 0.02-0.04 percent. 



Carbon monoxide removal was not included in the planning for Sealab II, as it was not ex- 

 pected that carbon monoxide would occur in significant concentrations. When carbon monoxide 

 levels of 20 parts per million or more were detected, two lithium hydroxide canisters were re- 

 placed with Hopcalite and silica gel for catalytic oxidation of carbon monoxide. This measure 

 appeared to lower the carbon monoxide to 10 to 15 parts per million (according to the rough 

 measurements available), and no further headaches were reported. 



Hydrocarbons and odors were controlled by the insertion of large filters of activated char- 

 coal into the atmosphere recirculating system. Samples of this charcoal bed have been sent to 

 NRL for further analysis. 



