18-16 Change A
U.S. Navy Diving Manual—Volume 4
excursion limit for 40 fsw. He may continue the dive, but he must maintain his
depth at 20 fsw or less and make no additional excursions.
NOTE
If the diver is unsure how long he was below 20 fsw, the dive must be
aborted.
18-4.6
Single-Depth Limits. The term Single-Depth Limits does not mean that the entire
dive must be spent at one depth, but refers to the time limit applied to the dive
based on the maximum depth attained during the dive.
18-4.6.1
Single-Depth Limits Definitions. The following definitions apply when using the
Single-Depth Limits:
Oxygen time is calculated as the time interval between when the diver begins
breathing from the closed-circuit oxygen UBA (on-oxygen time) and the time
when he discontinues breathing from the closed-circuit oxygen UBA (off-oxy-
gen time).
The depth for the dive used to determine the allowable exposure time is deter-
mined by the maximum depth attained during the dive. For intermediate depth,
the next deeper depth limit will be used.
18-4.6.2
Depth/Time Limits. The Single-Depth Limits are provided in Table 18-5. No
excursions are allowed when using these limits.
Example. Twenty-two minutes (oxygen time) into a compass swim, a dive pair
descends to 28 fsw to avoid the propeller of a passing boat. They remain at this
depth for 8 minutes. They now have two choices for calculating their allowed
oxygen time: (1) they may return to 20 fsw or shallower and use the time below 25
fsw as an excursion, allowing them to continue their dive on the Transit with
Excursion Limits to a maximum time of 240 minutes; or (2) they may elect to
remain at 28 fsw and use the 30-fsw Single-Depth Limits to a maximum dive time
of 80 minutes.
18-4.7
Exposure Limits for Successive Oxygen Dives. If an oxygen dive is conducted
after a previous closed-circuit oxygen exposure, the effect of the previous dive on
the exposure limit for the subsequent dive is dependent on the Off-Oxygen
Interval.
18-4.7.1
Definitions for Successive Oxygen Dives. The following definitions apply when
using oxygen exposure limits for successive oxygen dives.
Off-Oxygen Interval. The interval between off-oxygen time and on-oxygen
time is defined as the time from when the diver discontinues breathing from
his closed-circuit oxygen UBA on one dive until he begins breathing from the
UBA on the next dive.
