Dive_Man_ChangeA

21-24 Change A U.S. Navy Diving Manual—Volume 5 21-5.6.4.3 Carbon Dioxide Absorbent. CO₂ absorbent may be used beyond the expiration date, when used in a recompression chamber scrubber unit, when the recompres- sion chamber is equipped with a CO₂ monitor. When employed in a recompression chamber that has no CO₂ monitor, CO₂ absorbent in an opened but resealed bucket may be used until the expiration date on the bucket is reached. Pre-packed, double-bagged canisters shall be labeled with the expiration date from the absorbent bucket. 21-5.6.5 Temperature Control. If possible, internal chamber temperature should be main- tained at a level comfortable to the occupants. Cooling can usually be accomplished by chamber ventilation in accordance with paragraph 21-5.6.6. If the chamber is equipped with a heater/chiller unit, temperature control can usually be maintained for chamber occupant comfort under any external environmental conditions. Usually, recompression chambers will become hot and must be cooled continuously. Chambers should always be shaded from direct sunlight. The maximum durations for chamber occupants will depend on the internal chamber temperature as listed in Table 21-4. Never commit to a treatment table that will expose the chamber occupants to greater temperature/time combinations than listed in Table 21-4 unless qualified medical personnel who can evaluate the trade- off between the projected heat stress and the anticipated treatment benefit are consulted. A chamber temperature below 85°F (29.4°C) is always desirable, no matter which treatment table is used. Table 21-4. Maximum Permissible Recompression Chamber Exposure Times at Various Temperatures. Internal Temperature Maximum Tolerance Time Permissible Treatment Tables Over 104°F (40°C) Intolerable No treatments 95-104°F (34.4-40°C) 2 hours Table 5, 9 85-94°F (29.4-34.4°C) 6 hours Tables 5, 6, 6A, 1A, 9 Under 85°F (29.4°C) Unlimited All NOTE Internal chamber temperature can be kept considerably below ambient by venting or by using an installed chiller unit. Internal chamber temperature can be measured using electronic, bimetallic, alcohol, or liquid crystal thermometers. Never use a mercury thermometer in or around hyperbaric chambers. Since chamber ventilation will produce temperature swings during ventilation, the above limits should be used as averages when controlling temperature by ventilation. Always shade chamber from direct sunlight.