removal, and an electrical reheater. The air was dehinnidified by con- 

 densing water vapor on the heat exchanger coils, thus requiring reheat- 

 ing the air to the desired temperature of about 80° F. Relative 

 humidity was maintained between 45% and 55%. 



EMERGENCY AIR SYSTEMS 



Emergency air systems provided were a surface air supply system, a purge 

 system, a habitat emergency air supply system, a built-in breathing (BIB) 

 system, and escape air bottles. 



The surface emergency air supply was located at the surface support 

 center and consisted of four 240-SCF (at 2200 psi) compressed air 

 cylinders. This system served as a backup to the support center air 

 compressors . 



The purge system was designed to replace 90% of the habitat gas mixture 

 with air within 4 hours in the event of major contamination and then 

 equilibrate with nitrogen to the specified mixture. The system uses a 

 125-SCF/min, 100-psi diesel-driven air compressor and a nitrogen tube 

 trailer located at the support center to supply gas to the habitat via 

 the gas supply umbilical. In operation, air from the compressor would 

 replace habitat air until gas sampling indicated that all contaminates 

 had been removed. Nitrogen would then be introduced to the system to 

 reduce the PO2 to within allowable limits. This procedure was followed 

 on two occasions when electrical shorts occurred producing smoke. 

 Normal atmospheric conditions were established shortly after each purge. 



The habitat emergency air supply consisted of 23 240-standard cubic 

 feet (SCF) compressed air cylinders in the habitat base. This emergency 

 air supply could be activated by the crew in the event of normal air 

 supply failure. The system was designed so that the emergency air 

 would be introduced into the normal habitat air distribution system in 

 the event of topside compressor or umbilical failure. In the event of 

 atmospheric contamination within the habitat, the emergency air supply 

 could be valved directly to the BIB system. 



The BIB system provided 12 breathing stations within the habitat. In 

 this mode, air was available for 12 hours duration. The line pressure 

 to each BIB station was maintained at 100 psi, and demand regulator/ 

 hose assemblies and face masks were attached at each station. Of the 

 12 BIB stations, 4 were in the crew quarters, 4 were in the wet room, and 

 2 each were in the bridge and equipment rooms. Each BIB had a hose long 

 enough to reach the adjoining compartment. 



Eight escape air bottles with regulators, hoses, and mouthpieces were 

 available to provide capability to move about inside the habitat under 

 conditions requiring BIB breathing, and to escape from the habitat to 

 the personnel transfer capsule. Each bottle had an 18-SCF capacity, 



II-6 



