NITROX DIVING PROCEDURES
NITROX Diving Using Equivalent Air Depths. NITROX diving is based upon the
current U.S. Navy Air Decompression Tables. The actual schedule used is
adjusted for the oxygen percentage in the breathing gas. To use the EAD Decompression
Selection Table (Table 10-1), find the actual oxygen percentage of the
breathing gas in the heading and the diver’s actual depth in the left column to
determine the appropriate schedule to be used from the U.S. Navy Air Decompression
Tables. The EAD decompression schedule is where the column and row
intersect. Dives using NITROX may be used with any schedule from the U.S.
Navy Air Decompression Tables (No-Decompression Limits for Air, Standard Air
Decompression, Surface Decompression using Air or Surface Decompression
Using Oxygen). When using Table 10-1, round all gas mixtures using the standard
rounding rule where gas mixes at or above 0.5% round up to the next whole
percent and mixes of 0.1% to 0.4% round down to the next whole percent. Once an
EAD is determined and a Navy air table is selected, follow the rules of the Navy
air table using the EAD for the remainder of the dive.
Special Procedures. In the event there is a switch to air during the NITROX
dive, using the diver’s maximum depth and bottom time follow the U.S. Navy Air
Decompression Table for the actual depth of the dive.
Omitted Decompression. In the event that the loss of gas required a direct ascent
to the surface, any decompression requirements must be addressed using the standard
protocols for “omitted decompression.” For omitted decompression dives
that exceed the maximum depth listed on Table 10-1, the diving supervisor must
rapidly calculate the diver’s EAD and follow the omitted decompression procedures
based on the diver’s EAD, not his or her actual depth. If time will not permit
this, the diving supervisor can elect to use the diver’s actual depth and follow the
omitted decompression procedures.
Dives Exceeding the Normal Working Limit.The EAD Table has been developed
to restrict dives with a ppO2 greater than 1.4 ata and limits dive duration based on
CNS oxygen toxicity. Dives exceeding the normal working limits of Table 10-1
require the Commanding Officer’s authorization and are restricted to surfacesupplied
diving equipment only. All Equivalent Air Depths provided below the
normal working limit line have the maximum allowable exposure time listed
alongside. This is the maximum time a diver can safely spend at that depth and
avoid CNS oxygen toxicity. Repetitive dives are not authorized when exceeding
the normal working limits of Table 10-1.
