15-20
U.S. Navy Diving Manual—Volume 3
As a general guideline to achieve optimum comfort for all divers, the temperature
should be kept low enough for the warmest diver to be comfortable. Cooler divers
can add clothing as needed. All divers should be questioned frequently about their
comfort.
The relative humidity should be maintained between 30 and 80 percent with 50 to
70 percent being the most desirable range for diver comfort, carbon dioxide
scrubber performance, and fire protection.
15-17
FIRE ZONE CONSIDERATIONS
Every effort shall be made to eliminate any fire hazard within a chamber. When
oxygen percentages are elevated as during the later stages of decompression, a fire
will burn rapidly once started, perhaps uncontrollably. As a result, special precau-
tions are necessary to protect the diver’s safety when in the fire zone. The fire zone
is where the oxygen concentration in the chamber is 6 percent or greater. Using
standard saturation diving procedures (oxygen partial pressure between 0.44 and
0.48 ata), fire is possible at depths less than 231 fsw. Thus, during a saturation
dive the divers will be in the fire zone during initial compression to depth and
during the final stages of decompression.
Example. The chamber atmosphere is 0.48 ata ppO2. The minimum oxygen
percentage for combustion is 6 percent. Compute the fire zone depth.
The fire zone depth is computed as follows:
Although the design of the DDS minimizes fire potential, personnel must remain
vigilant at all times to prevent fires. Appropriate precautions for fire prevention
include:
Fire-suppression systems, if available, must be operational at all times when in
the fire zone.
Chamber clothing, bed linen, and towels shall be made of 100% cotton. Diver
swim trunks made of a 65% polyester–35% cotton material is acceptable.
Mattresses and pillows shall be made of fire-retardant material when in the fire
zone.
Limit combustible personal effects to essential items.
Limit reading material, notebooks, etc., in the fire zone.
Fire zone depth (fsw)
ppO2
33
O2%/100
--------------------------
33
–
=
0.48
33
0.06
----------------------
33
–
=
231 fsw
=
