22-16 Change A
U.S. Navy Diving ManualVolume 5
Gag Valves. The actuating lever of the chamber gag valves shall be maintained in
the open position at all times, during both normal chamber operations and when
the chamber is secured. The gag valves must be closed only in the event of relief
valve failure during chamber operation. Valves are to be lock-wired in the open
position with light wire that can be easily broken when required. A WARNING
plate, bearing the inscription shown below, shall be affixed to the chamber in the
vicinity of each gag valve and shall be readily viewable by operating personnel.
The WARNING plates shall measure approximately 4 inches by 6 inches and read
Ventilation. The basic rules for ventilation are presented below. These rules
permit rapid computation of the cubic feet of air per minute (acfm) required under
different conditions as measured at chamber pressure (the rules are designed to
ensure that the effective concentration of carbon dioxide will not exceed 1.5
percent (11.4 mmHg) and that when oxygen is being used, the percentage of
oxygen in the chamber will not exceed 25 percent).
When air is breathed, provide 2 cubic feet per minute (acfm) for each diver at
rest and 4 cubic feet per minute (acfm) for each diver who is not at rest (i.e., a
tender actively taking care of a patient).
When oxygen is breathed from the built-in breathing system (BIBS), provide
12.5 acfm for a diver at rest and 25 acfm for a diver who is not at rest. When
these ventilation rates are used, no additional ventilation is required for
personnel breathing air. These ventilation rates apply only to the number of
people breathing oxygen and are used only when no BIBS dump system is
If ventilation must be interrupted for any reason, the time should not exceed 5
minutes in any 30-minute period. When ventilation is resumed, twice the
volume of ventilation should be used for the time of interruption and then the
basic ventilation rate should be used again.
If a BIBS dump system is used for oxygen breathing, the ventilation rate for
air breathing may be used.
If portable or installed oxygen and carbon dioxide monitoring systems are
available, ventilation may be adjusted to maintain the oxygen level below 25
percent by volume and the carbon dioxide level below 1.5 percent surface
Chamber Ventilation Bill. Knowing how much air must be used does not solve the
ventilation problem unless there is some way to determine the volume of air actu-
ally being used for ventilation. The standard procedure is to open the exhaust
The gag valve must remain open at all times.
Close only if relief valve fails.