Is the Hollis Prism 2 Rebreather Right for You?

Rick Harkins   Aug 12, 2026

scuba gear scuba equipment rebreathers hollis prism

If you've been diving open-circuit for a while, you've probably heard other divers talk about rebreathers: longer bottom times, no bubbles, way less gas used per dive. It sounds great, but it's also a real jump in complexity and cost, so it's worth understanding what you're actually getting into before you commit. As an authorized Hollis Prism 2 dealer and service facility, we get asked about this a lot. Here's the plain-language version.

What a rebreather actually does differently

A standard scuba regulator dumps every breath you exhale straight into the water as bubbles. A rebreather doesn't waste it. Instead, it recycles your breathing gas: scrubbing out the carbon dioxide you exhale and adding back just enough oxygen to keep the mix breathable. That's the whole trick, and it's why rebreather diving means longer dive times, no bubbles to spook marine life, and a much smaller gas footprint for the same dive.

It's also a serious step up in complexity compared to open-circuit gear, which is exactly why buying, learning, and servicing one should go through a dealer who actually knows the unit inside and out, not just someone selling boxes.

Why the Prism 2 specifically

The Prism 2 is built by Hollis, a well-known name in the technical diving world, and it's designed around redundancy and diver control rather than fully automated black-box operation. That matters, because on a rebreather, you want to understand what your unit is doing and why, not just trust a light to turn green.

The breathing loop

At the center of the unit is the breathing loop, the closed path your air travels as you breathe in and out. It starts at a keyed, one-way mouthpiece with mushroom check valves on either side, whose only job is making sure your breath moves in one direction around the loop instead of doubling back on itself.

The scrubber

Somewhere in that loop, the carbon dioxide you exhale has to get removed before the gas comes back to you. On the Prism 2, that's a radial flow scrubber canister mounted vertically on a backplate, sitting right between the unit's twin supply cylinders, one for oxygen and one for diluent gas.

Counterlungs

The Prism 2 uses dual, front-mounted counterlungs as a flexible gas reservoir, sized to match your own lung volume so breathing stays easy at depth. Each one has automatic and manual gas addition, plus a variable volume control valve for venting gas on ascent or purging the loop. As you descend, increasing pressure collapses the counterlung against a valve actuator that automatically adds diluent, so you're not manually managing that on every dive.

Electronics and displays

The electronics, sensors, and batteries live in a head assembly at the top of the scrubber. You get two independent displays: an analog LED primary display for a quick read on status and alarms, and a digital OLED secondary display that cross-checks everything the primary is telling you, plus battery status and your current set point. Behind the scenes, the system "votes" between three separate oxygen sensors and uses that consensus to control the oxygen solenoid, keeping your gas mix where it should be.

How it's built and tested

This is the part that matters most when your life depends on gear working correctly every single dive:

• Every unit is 100% hand-assembled and tested in-house in Salt Lake City, Utah, including a pressure test to 300 feet before it ships
• Hollis Rebreathers holds a Module C2 Certificate from SGS, meaning its systems and processes are independently audited every year
• Critical oxygen components are certified to ASTM G93 Level B and meet MIL-STD-1330
• The Prism 2 is CE approved for sale and training in the UK and EU, and both counterlung variants meet the EN 14143:2013 standard, the European benchmark for rebreather safety

What it takes to actually dive one

Rebreather diving requires dedicated certification beyond standard open-circuit training, and the unit needs bi-annual servicing to keep performing safely and reliably. That's not a knock against the Prism 2, it's just the reality of closed-circuit diving in general. If you're the kind of diver who's comfortable with more pre-dive checks and ongoing maintenance in exchange for longer, quieter dives, it's worth a serious look.

Talk to a dealer who actually services these

We're an authorized Hollis Prism 2 dealer and a full-service, full-repair facility for the unit, right here near Harrisburg, PA. Whether you're shopping for your first rebreather, ready to make the jump from open-circuit, or already own a Prism 2 and need your bi-annual service, our team can walk you through it. Learn more about Prism 2 sales and service or call us at (833) PA DIVER.