Normal And Maximum Limits For Air Diving

Depth fsw (meters)

Limit for Equipment

Notes

60 (18)

MK 21 MOD 0 diving equipment, maximum working limit without Emergency Gas Supply (EGS)

a

60 (18)

MK 20 MOD 0 equipment surface-supplied

a

60 (18)

Maximum depth for standby scuba diver using a single cylinder

100 (30)

Open-circuit scuba with single scuba bottle

b

130 (40)

Open-circuit scuba, normal working limit

b

190 (58)

Open-circuit scuba, maximum working limit with Commanding Officer's permission

b, d

190 (58)

MK 21 MOD 1 (air) diving equipment with EGS, normal working limit

c, d, e

285 (87)

MK 21 MOD 1 (air) diving equipment with EGS, maximum working limit, exceptional exposure with authorization from the Chief of Naval Operations (N873)

c, d, e

General Operating Notes (Apply to all):

1. These limits are based on a practical consideration of working time versus decompression time and oxygen-tolerance limits. These limits shall not be exceeded except by specific authorization from the Chief of Naval Operations (N873).

2. Do not exceed the limits for exceptional exposures for the Standard Air Decompression Table.

3. In an emergency, any operable recompression chamber may be used for treatment if deemed safe to use by the Diving Supervisor.

Specific Notes:

a. When diving in an enclosed space an EGS must be used by each diver.

b. Under normal circumstances, do not exceed the limits of the No-Decompression Table. Dives requiring decompression may be made if considered necessary with approval by the Commanding Officer of the diving command. The total time of a scuba dive (including decompression) shall not exceed the duration of the apparatus in use, disregarding any reserves.

c. A Diving Medical Officer is required at the site for all air dives deeper than 190 fsw, where the maximum working depth of the diving apparatus may be exceeded, and for exceptional exposure dives.

d. All planned air decompression dives deeper than 130 fsw require a certified recompression chamber on site. An on-site chamber is defined as a certified and ready chamber accessible within 30 minutes of the dive site by available transportation.

e. The Exceptional Exposure Tables, printed in red in the Standard Air Tables, have a significantly higher probability of DCS and CNS oxygen toxicity.

Figure 6-14. Normal and Maximum Limits for Air Diving.

Figure 6-14. Normal and Maximum Limits for Air Diving.

The increase of air consumption with depth limits open-circuit scuba to 130 fsw for reasonable working dives. The hazards of nitrogen narcosis and decompression further limit open-circuit scuba to 190 fsw even for short duration dives. Surface-supplied equipment is generally preferred between 130 and 190 fsw, although open-circuit scuba may be used under some circumstances. Decompression scuba dives and scuba dives deeper than 130 fsw may be conducted when dictated by operational necessity and with the specific approval of the Commanding Officer. All open-circuit scuba dives beyond 100 fsw shall employ twin cylinders, with each having a capacity at least equal to a steel 72 cylinder (64.7 cubic feet).

In some operations there may be no clear-cut choice of which diving technique to use. Selecting a diving technique may depend upon availability of equipment or trained personnel. The following comparison of scuba and surface-supplied techniques highlights the significant differences between the methods and outlines the effect these differences will have on planning.

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