Owner`s manual

Dive Rite

Ch. 1 Pg. 4

SC Semi-Closed

SCR Semi Closed Rebreather

WOB Work of Breathing

Scuba System Overview

The Open-Circuit Scuba system is the configuration that is usually associated with scuba diving

and the configuration used by the average recreational diver. This chapter will introduce the

semi-closed and closed-circuit rebreather designs or more simply, SCR and CCR.

In the past, the use of rebreathers were primarily the domain of the military with some limited

use by the scientific and commercial diving communities. The recreational and scientific diving

communities have traditionally used open-circuit scuba systems due to its simplicity, low

operating cost, low initial investment and ease of training. The commercial diving community

has primarily used a surface-supplied configuration that allows for two-way communication, and

unlimited gas supply through an umbilical connection to the surface. The use of rebreathers by

commercial diving operations has been increasing due to rising costs associated with continuous

gas production.

Over the last decade the use of rebreathers by the recreational diving community has increased

significantly due to the advent of user friendly systems, increased reliability, increased

availability of support materials, broader choice of rebreathers and reduced cost. Continuing

growth is expected in the coming years as additional manufacturers enter the market and the

technology is exposed to a greater diversity of divers. Over the last several years many

outspoken opponents to rebreathers have become advocates as they realize that rebreathers are

ideal tools and increase safety in many situations. Rebreathers are often thought of as new and

unproven technology even though rebreathers predate traditional scuba by over 50 years.

Rebreathers have gained the greatest acceptance in the deep diving/exploration communities and

those involved with underwater video and photography. The reduction of bubbles allow a more

natural interaction with marine life and a reduced environmental impact. The depth independent

duration allows longer and deeper dives without compromising safety.

Open-Circuit Systems

This is the traditional SCUBA configuration. A high pressure gas

stored in a cylinder and is reduced in two steps to deliver a

breathing gas at ambient pressure. The first step reduces the

cylinder pressure to a fixed intermediate pressure with respect to

ambient pressure and the second step reduces this intermediate

pressure to ambient pressure. Gas is inspired by means of a

demand valve and is expelled into the surrounding environment.