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ZHL-16C, VPM-B, RGBM, DSAT, VVAL-18M ... Does It Really Matter?

At the risk of annoying those who do have a preference for a specific decompression algorithm, the simple answer for most divers is NO the algorithm is not critical. There is no expert consensus that any one of the current crop of decompression algorithms is better than another. All of these algorithms used in dive computers and desktop table generation software, when set to their default conservancy values, will get you out of the water with an acceptable margin of safety. Among technical divers, the recent trend has been toward significantly deeper initial stops, based mostly on anecdotal reports within the community that some divers 'feel better' after such dives. Yet some experts feel deep stops may be counter productive, an example of the lack of consensus.

Numerous variants of ZHL-16C are very widely implemented in both sport and technical dive computers. For technical diving, versions of ZHL-16C that include user configurable Gradient Factor modifications are very popular because the GF values can be used to generate deeper initial stops. VPM-B dive profiles typically also have deeper initial stops, along with reduced time at shallow depths resulting in a 'smoother' profile. Some divers believe the reduced shallow depth stop times may be too short for lengthy VPM-B profiles; the VPM-B/E and VPM-B/GFS variations exist to address this concern. RGBM (basis for NAUI tables with its roots in VPM) and DSAT (basis for PADI tables) are most often seen in no stop required sport diving applications. VVAL-18M is the basis for the modern US Navy Tables.

The most important safety factor is not the algorithm you select, rather that you follow very closely the recommendations of that algorithm and safe diving in general. Regardless of the decompression algorithm you use, it would be unwise to immediately surface once you have cleared your required decompression stop obligations. Doing so would result in your surfacing with the absolute maximum saturation allowed by the algorithm you selected, i.e. incurring the maximum risk. For stop required diving, as with sport no stop required diving, after clearing your required decompression you should always perform an additional 3 to 5 minute 'safety stop' at your last stop depth.

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