Sample Time Limits

As is discussed in the Ascending From A Dive article, the first step in comparing dive tables or software is to first determine the no-stop time limits to determine their conservatism. A good way to determine how conservative (or aggressive) a dive table or software is, one should investigate not the no-stop time limits at the deeper depths, but at the middle to shallower depths. Below are some comparisons between the time limits given by both Departure and V-Planner.

V-Planner is modeled after the VPM model with their VPM-B model having some more conservative adjustments to the model. While some individuals may disagree, the VPM model is very similar to the RGBM model since the RGBM model is simply an extension of the VPM model. As can be seen, starting at 60 feet and deeper, Departure offers the flexibility of having either more conservative or more aggressive time limits than V-Planner, thus giving the diver a choice in how to plan their dive. The interesting thing to note are the shallow time limits of V-Planner. The shallower the time limits, the more they deviate from "accepted" time limits. For example, it is well known that a saturation depth (minimum bends depth) is shallower than 30 feet (and is closer to 20 feet), but V-Planner allows for such a dive to occur. While a diver may never do such a dive, it shows that the model is extremely aggressive and allows for some very high nitrogen/gas tissue tensions upon surfacing, especially in the "slower compartments".

	VPM-B Nominal	VPM-B + Four	1.00	1.20	1.30	1.50	2.00	DCIEM (1992)	Bassett
Depth (feet)	MBD:30'	23'	20'	19'	18'	17'	15'
25 30 35 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180	99999 99999 1291 322 99 53 33 24 18 15 12 10 8 6 5 5 4 4	14549 556 207 118 58 36 25 18 14 11 9 7 6 5 5 4 3 3	521 300 201 146 89 60 43 32 25 20 16 13 11 9 8 7 6 5	448 264 180 130 79 53 38 29 22 18 14 12 10 8 7 6 5 5	409 244 167 123 74 50 36 27 21 17 14 11 9 8 7 6 5 5	342 211 146 108 66 45 32 24 19 15 12 10 8 7 6 5 4 4	226 146 103 77 47 32 23 17 13 10 8 7 5 4 4 3 3 3	300 150 75 50 35 25 20 15 12 10 8 7 6 6 5 5	220 120 70 50 40 30 25 20 15 12

Note:
The V-Planner has five different sets of time limits when using the VPM-B model. The nominal setting is the most aggressive and the + Four setting is the most conservative setting of V-Planner. The above V-Planner time limits are based upon the following: Version 3.22, dive altitude is sea level, post dive altitude is 0 feet, the water is sea water, the descent rate is 150 feet per minute, the ascent rates are 30 feet per minute.

Departure offers 100 different time limit settings in the form of a sliding scale in addition to being able to completely customize the time limits you wish to model. The 1.00 setting gives the least conservative times available. The 1.50 is the middle set of time limits available and the 2.00 is the most conservative set of time limits available. The time limits are based upon: a sea level dive, a post dive altitude of 0 feet, a descent rate of 150 feet per minute, and sea water for the dive.

While there are more modern time limits, Dr. Bruce Bassett’s are presented as they are consistent with other time limits and because we wished to give recognition to Dr. Bassett’s early involvement in sport diving.

	100	120	150	1.00	1.20	1.30	1.50	2.00	DCIEM (1992)	Bassett
Depth (feet)	MBD:23'	23'	21'	20'	19'	18'	17'	15'
25 30 35 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180	2309 849 325 176 87 58 40 30 23 18 15 12 11 10 9 8 6 6	2309 848 323 175 87 57 40 29 22 18 14 12 10 9 8 8 7 6	2353 947 455 253 110 61 40 28 21 17 14 12 10 9 8 7 7 7	521 300 201 146 89 60 43 32 25 20 16 13 11 9 8 7 6 5	448 264 180 130 79 53 38 29 22 18 14 12 10 8 7 6 5 5	409 244 167 123 74 50 36 27 21 17 14 11 9 8 7 6 5 5	342 211 146 108 66 45 32 24 19 15 12 10 8 7 6 5 4 4	226 146 103 77 47 32 23 17 13 10 8 7 5 4 4 3 3 3	300 150 75 50 35 25 20 15 12 10 8 7 6 6 5 5	220 120 70 50 40 30 25 20 15 12

Note:
The Abyss has three different sets of time limits depending upon which decompression model is chosen. The above Abyss time limits are based upon the following: Version 2.01, dive altitude is sea level, post dive altitude is 0 feet, the water is sea water, the descent rate is 150 feet per minute, the ascent rates are the default settings, and the physiology is the default setting and equals 75. Abyss is a registered Trademark of Abysmal Diving Inc.

Departure offers 100 different time limit settings in the form of a sliding scale in addition to being able to completely customize the time limits you wish to model. The above five sets were chosen as examples. The 1.00 setting gives the least conservative times available. The 1.50 is the middle set of time limits available and the 2.00 is the most conservative set of time limits available. The time limits are based upon: a sea level dive, a post dive altitude of 0 feet, a descent rate of 150 feet per minute, and sea water for the dive.

While there are more modern time limits, Dr. Bruce Bassett’s are presented as they are consistent with other time limits and because we wished to give recognition to Dr. Bassett’s early involvement in sport diving.