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The PRISM Topaz Rebreather

PRISM Topaz Underwater Breathing Apparatus

PRISM Topaz is a closed-circuit mixed gas underwater breathing apparatus (frequently called a "rebreather") designed specifically for the recreational diving marketplace. The PRISM Topaz model is the first of a new series of "third generation" PRISM rebreathers. As such, PRISM Topaz also serves as the development testbed for additional models based on third generation PRISM technology. Models optimized for deep diving andfor military applications will be developed from the PRISM Topaz foundation. This document presents the design goals and specifications of PRISM Topaz.

PRISM Topaz Application Considerations

Serving as a final development testbed for the third generation PRISM, the initial PRISM Topaz units will beoperated by Steam Machines at its training center on Cayman Brac and elsewhere only under direct supervisionof Steam Machines personnel. The units will be used by openwater certified divers in conjunction with Steam Machines "Closed Circuit Diver’ certification courses. This will be the first widespread use of such mixed gas closed circuit diving equipment by personnel who have not had extensive military or commercial training.

It is Steam Machines’ intent to maintain tight control of the operation of all PRISM Topaz units during this critical final "real world" test phase. The units are fitted with onboard digital data loggers and will be maintained by Steam Machines technicians. Regular performance and application suitability evaluations will be performed throughout the operational test phase. This evaluation phase will provide Steam Machines with invaluable data pertaining to actual use of closed-circuit diving systems (and, more specifically the use of PRISM Topaz) in the real world by civilian personnel. Final unit design review will incorporate changes that may result from analysis of this operational evaluation.

Steam Machines will set operational limits on the PRISM Topaz units used at the Steam Machines training centers. These limits will be targeted at operator, rather than hardware, capability considerations. Such operational limitations will include an operational depth limitation of 150fsw. Steam Machines test divers will perform manned testing of all PRISM Topaz units outside the restricted recreational diver test envelope. In addition, unmanned and manned testing beyond recreational limits is being undertaken in conjunction with various military projects.

PRISM Topaz Flexible Platform Considerations

PRISM Topaz is designed specifically for the recreational marketplace. An overwhelming design consideration for this market is unit size and ease of use. Extreme dive duration was sacrificed in exchange for overall small form factor and light weight. PRISM Topaz weighs about 38 pounds…about the same as an 80 cubic foot open circuit diving rig.

The PRISM Topaz design, however, is very flexible, allowing reconfiguration to more demanding applications with minimal component change. All breathing loop components are designed for minimal work-of-breathing at extreme depths. All major PRISM Topaz components are designed with an operational depth limitation goal of 500 fsw. Minor additional component changes could extend this depth. Since the PRISM Topaz series platform is designed to physically perform well at 500 fsw, minimum performance specifications of the PRISM Topaz version are determined primarily by gas cylinder and scrubber size.

The unique design of the PRISM Topaz series platform allows large increases in operational range by simple increase of gas cylinder size and scrubber length. A deep diving version of the PRISM Topaz will enter field testing by Steam Machines concurrently with final PRISM Topaz operational trials.

PRISM Topaz Operational Design Specification

Operating modes:

Major physical components:


Physical Specifications:

‡ Steam Machines solid state scrubber technology is currently under development. All performance figures are preliminary.

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435 North Pacific Coast Highway Suite 150 - Redondo Beach, California 90277 - Tel 310.937.7556 Fax 310.937.7555 -

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Revised: December 01, 2002.
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