Winter2016AlertDiver

WINTER 2016

the line is crossed without injury the rule will become

less important. After it has been crossed a few times

the rule may seem irrelevant, or the individual may

perceive himself or herself as being endowed with

special protection. Both of these viewpoints can lead

to poor choices. Flipping the focus to “do this and

be safer” can provide much healthier reinforcement.

When nothing bad happens, the positive benefits of the

practice are reinforced. Both peace of mind and good

practice are promoted.

Avoid mission creep.

Even the best intentions can

be pushed aside by trouble-free diving and personal

comfort. This can be exemplified on multiday dive

trips. The intensity of diving frequently increases as

the trip continues. It is not uncommon for a person

developing DCS during a trip to describe their most

conservative practice as their norm. Electronic dive

logs, however, frequently show an erosion of safety

buffers over successive days.

Pick your partners well.

The mindset and practice of

others in your group can radically affect your risk.

Choosing those with complementary goals, objectives

and attitudes can help ensure that the activity remains

within your comfort zone. If someone you are

diving with pushes you beyond your comfort zone,

remember the first two rules: Know the risk, and take

responsibility for your own safety.

Use tools to defend your practice.

Selecting appropriate

conservatism settings on your dive computer can reduce

the need to argue over no-decompression limits or

decompression profiles. Going back to the faith we often

have in computers, differences in the selected settings

may prompt discussions that help everyone gain insight.

A critical mind is essential at this point to weigh the

merits of the often heartfelt beliefs of those participating

in the debate. Understanding the available tools is

important for understanding the options and levels of

conservativism. An article about gradient factors in the

Fall 2015 issue of

Alert Diver

might be helpful to this end.

PRACTICAL STRATEGIES

Solid knowledge, awareness, critical thinking and

smart partner selection provide the foundation for

good diving practice. Implementation requires further

thought. Employing a number of small buffers can

produce a web of protections that can mean giving up

little in the way of opportunity while maintaining a

high degree of conservatism.

The dive profile is the single most important

determinant of the ultimate decompression risk of

a dive. The shift from square profiles to multilevel

profiles can produce powerful advantages.

Going deep increases the rate of inert gas uptake and

the ultimate amount to be eliminated, but going to the

extremes of one’s training can be enticing. Multilevel

diving offers a good way to scratch that itch while

maintaining good decompression safety. Choosing sites

appropriate for multilevel dives is a great way to start.

In the simplest case, swimming outbound at one depth

and back at a shallower depth can limit inert gas uptake

and extend the controlled inert gas elimination period.

Decompression stress is minimized, and the diver can

experience different zones during a single dive.

Out and back is fine for many recreational exposures,

but as maximum depths increase, it becomes increasingly

important to spend progressively more time at

progressively shallower depths. Dive sites that make this

easy facilitate optimized dive profiles.

The high relative rate of pressure change in the

shallowest zone makes it critical in determining the

overall decompression stress. Next to backing off the

intensity of a dive, the most important decompression

safety buffer is time spent in the shallow regions

during ascent. For much recreational diving this can

be considered the depth range shallower than 25 feet.

The popularization of the safety stop was probably the

Choose dive partners whose risk tolerance,

goals and attitudes align with your own.

The popularization of the safety stop was

probably the most significant evolution

in decompression safety for recreational

diving in the past 30 years.

STEPHEN FRINK