Is the protocol always 20/85, or does it vary with situation?
Although it is not as deep as has been used by some in the past, 20/85 is still a deeper stop profile than those being used by a number of other people these days. Here is a dive with 20/85 and then one with 50/85. The 20/85 profile's first stop is 30 feet deeper than the 50/85. It has 4 more minutes decompressing on back gas before the 70 foot switch, and it adds 2 minutes at the shallow depths to compensate.
MultiDeco 4.14 by Ross Hemingway,
ZHL code by Erik C. Baker.
Decompression model: ZHL16-C + GF
DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = GF 20/85
Dec to 200ft (3) Trimix 18/45 60ft/min descent.
Level 200ft 26:40 (30) Trimix 18/45 1.24 ppO2, 76ft ead, 95ft end
Asc to 130ft (32) Trimix 18/45 -30ft/min ascent.
Stop at 130ft 0:40 (33) Trimix 18/45 0.87 ppO2, 43ft ead, 56ft end
Stop at 120ft 1:00 (34) Trimix 18/45 0.82 ppO2, 38ft ead, 51ft end
Stop at 110ft 1:00 (35) Trimix 18/45 0.76 ppO2, 33ft ead, 45ft end
Stop at 100ft 1:00 (36) Trimix 18/45 0.71 ppO2, 29ft ead, 40ft end
Stop at 90ft 2:00 (38) Trimix 18/45 0.66 ppO2, 24ft ead, 34ft end
Stop at 80ft 3:00 (41) Trimix 18/45 0.60 ppO2, 19ft ead, 29ft end
Stop at 70ft 2:00 (43) Nitrox 50 1.53 ppO2, 32ft ead
Stop at 60ft 3:00 (46) Nitrox 50 1.38 ppO2, 26ft ead
Stop at 50ft 4:00 (50) Nitrox 50 1.24 ppO2, 19ft ead
Stop at 40ft 5:00 (55) Nitrox 50 1.09 ppO2, 13ft ead
Stop at 30ft 8:00 (63) Nitrox 50 0.94 ppO2, 7ft ead
Stop at 20ft 10:00 (73) Oxygen 1.59 ppO2, 0ft ead
Stop at 10ft 20:00 (93) Oxygen 1.29 ppO2, 0ft ead
Surface (93) Oxygen -20ft/min ascent.
OTU's this dive: 122
CNS Total: 52.6%
Gas density: 5.1g/l
168.7 cu ft Trimix 18/45
30.0 cu ft Nitrox 50
25.1 cu ft Oxygen
223.8 cu ft TOTAL
MultiDeco 4.14 by Ross Hemingway,
ZHL code by Erik C. Baker.
Decompression model: ZHL16-C + GF
DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = GF 50/85
Dec to 200ft (3) Trimix 18/45 60ft/min descent.
Level 200ft 26:40 (30) Trimix 18/45 1.24 ppO2, 76ft ead, 95ft end
Asc to 100ft (33) Trimix 18/45 -30ft/min ascent.
Stop at 100ft 0:40 (34) Trimix 18/45 0.71 ppO2, 29ft ead, 40ft end
Stop at 90ft 1:00 (35) Trimix 18/45 0.66 ppO2, 24ft ead, 34ft end
Stop at 80ft 3:00 (38) Trimix 18/45 0.60 ppO2, 19ft ead, 29ft end
Stop at 70ft 2:00 (40) Nitrox 50 1.53 ppO2, 32ft ead
Stop at 60ft 2:00 (42) Nitrox 50 1.38 ppO2, 26ft ead
Stop at 50ft 4:00 (46) Nitrox 50 1.24 ppO2, 19ft ead
Stop at 40ft 5:00 (51) Nitrox 50 1.09 ppO2, 13ft ead
Stop at 30ft 8:00 (59) Nitrox 50 0.94 ppO2, 7ft ead
Stop at 20ft 10:00 (69) Oxygen 1.59 ppO2, 0ft ead
Stop at 10ft 18:00 (87) Oxygen 1.29 ppO2, 0ft ead
Surface (87) Oxygen -20ft/min ascent.
OTU's this dive: 115
CNS Total: 50.3%
Gas density: 5.1g/l
161.4 cu ft Trimix 18/45
28.4 cu ft Nitrox 50
23.6 cu ft Oxygen
213.4 cu ft TOTAL