VVal-18 and VVal-18M Air Decompression Tables

By Rubicon Foundation editorial team

6 min read · 22 October 2026

VVal-18 and VVal-18M Thalmann Algorithm – air decompression tables and procedures is a 2007 technical report by Gerth WA and Doolette DJ, published in Navy Experimental Diving Unit. It addresses algorithm-based planning for decompression after air dives, a central challenge in managing the ascent from elevated pressure while limiting decompression illness risk.

What is an air decompression table designed to do?

At depth, the pressure of breathing gas drives inert gas, chiefly nitrogen in air, into the body’s tissues. As a diver ascends and pressure falls, dissolved gas leaves those tissues and is carried away; the rate of this process varies among tissues and depends on the dive profile.

A decompression table turns a model of gas uptake and elimination into a practical schedule. It sets out ascent constraints and, where required, pauses at shallower depths so that pressure is reduced in stages rather than all at once.

The title identifies the subject as air decompression tables and procedures built around the VVal-18 and VVal-18M Thalmann algorithms. The focus is therefore not simply depth, but how a computational model is translated into usable guidance for a planned ascent.

How does an algorithm inform staged ascent?

Decompression algorithms represent the body as theoretical compartments with different rates of inert-gas exchange. These compartments are a way to model tissue behaviour; they are not literal anatomical structures. A calculation tracks loading during descent and time at depth, then estimates constraints on ascent as the diver returns toward surface pressure.

A model must balance competing concerns. An ascent that is too rapid can promote bubble formation and decompression stress, while longer or more restrictive schedules carry costs in time, gas use and operational complexity. No mathematical model can capture every individual or environmental factor perfectly.

Inert-gas loading: pressure and exposure time influence how much nitrogen enters the body.
Tissue kinetics: different model compartments absorb and release gas at different rates.
Ascent control: staged stops or depth limits regulate pressure reduction.
Operational procedure: a table must be interpreted and followed under real diving conditions.

Why do decompression procedures matter in diving?

Decompression planning matters wherever a dive can load tissues with enough inert gas to make an unrestricted ascent inappropriate. The consequences of inadequate decompression can include decompression illness, which may affect the nervous system, joints, skin, lungs or other parts of the body.

For divers, a table provides a structured plan rather than a guess about how quickly to ascend. For diving physicians and hyperbaric clinicians, decompression models help frame the physiological circumstances surrounding a dive, although a model or schedule cannot diagnose or treat an individual’s symptoms.

Scientific and operational diving also depend on procedures that can be understood, communicated and carried out consistently. Planned stops, gas supply, workload, environmental conditions and the possibility of a changed dive profile all affect whether a schedule can be followed safely.

Where does the Thalmann approach fit in decompression research?

Decompression research has long sought practical ways to connect pressure exposure with the changing gas burden in the body. Algorithmic tables belong to this broader effort: they make a physiological model operational by converting an exposure profile into ascent rules.

Comparing algorithms and procedures is part of the wider study of decompression risk, model assumptions and usability. Researchers examine how schedules represent tissue kinetics and how their instructions work in the settings where divers must apply them. A table is one tool within a larger safety system, not a guarantee against injury.

The publication’s venue, Navy Experimental Diving Unit, places its subject in the technical domain of diving procedures and decompression planning. Its title identifies the VVal-18 and VVal-18M versions of the Thalmann algorithm as the focus, alongside their associated air tables and procedures.

What should readers keep in mind when using decompression tables?

Tables apply to defined conditions and assumptions. A diver should use the procedure appropriate to the planned dive and training, account for the actual profile, and avoid treating a schedule as permission to exceed its limits or as a substitute for sound dive planning.

Decompression illness can occur despite adherence to a planned schedule, and symptoms after diving require prompt assessment. A diving-medicine physician should be consulted for medical concerns; suspected decompression illness warrants urgent professional evaluation.

Frequently asked questions

What does “air decompression table” mean?

It is a planned schedule that sets ascent limits and any required stops for a dive using air, based on a decompression model and defined dive conditions.

Why are decompression stops used?

Stops allow pressure to fall in stages, giving inert gas more time to leave the body during ascent. Their role depends on the applicable schedule and dive profile.

Can a decompression table guarantee that illness will not occur?

No. Tables support planning but cannot account perfectly for every diver or circumstance. Symptoms after a dive need prompt assessment by qualified medical professionals.

Citation details

Title: VVal-18 and VVal-18M Thalmann Algorithm – air decompression tables and procedures
Authors: Gerth WA; Doolette DJ
Year: 2007
Published in: Navy Experimental Diving Unit
Identifiers: NEDU TR 07-09
Record type: Technical report
Repository record: Rubicon Research Repository, handle 123456789/8349

This page is an original summary written by the Rubicon editors from the publication’s bibliographic record. It does not reproduce the paper, its abstract or its data; consult the publication itself for its methods and findings.