The quiet hum of your breathing loop, the steady glow of three green sensor readings, the confidence that every component is performing exactly as designed — this is what a well-maintained rebreather feels like underwater. That assurance does not happen by accident. It is the result of a disciplined maintenance routine that begins long before you reach the dive site and extends well beyond rinsing your gear at the end of the day.
Closed-circuit rebreathers demand a level of care that goes far beyond what most divers are accustomed to with open-circuit equipment. AP Diving designs the Inspiration and Evolution platforms with maintainability at their core, but the responsibility for following a structured service schedule ultimately falls on you. This guide walks through every layer of rebreather maintenance — from daily pre-dive checks to annual factory service — so you know exactly what to do, when to do it, and when to call in the professionals.
Why Rebreather Maintenance Is Different from Open-Circuit Gear
Open-circuit scuba equipment is mechanically straightforward. A regulator reduces tank pressure, delivers gas on demand, and exhausts your breath into the water. Maintenance typically means an annual regulator service and occasional visual inspections of your cylinder. The consequences of a minor oversight are usually limited — a free-flowing regulator is inconvenient, but it rarely puts you in immediate danger if you manage your gas supply responsibly.
A rebreather operates on fundamentally different principles. It recirculates your breathing gas through a chemical scrubber that removes carbon dioxide, adds oxygen to maintain a target partial pressure, and monitors the loop environment with electronic sensors. Each of these subsystems must function correctly for the unit to sustain life. A degraded oxygen sensor can deliver a hypoxic or hyperoxic mix without warning. A compromised scrubber canister can allow CO2 to pass through unchecked. A leaking counterlung can flood your breathing loop. The stakes are higher, and the maintenance schedule reflects that reality.
AP Diving addresses this complexity through modular design. Components are engineered for easy removal, inspection, and replacement at the user level — a deliberate philosophy that encourages hands-on ownership of your equipment. But modularity only works if you understand the maintenance framework and follow it consistently. If you are just getting started with rebreather care, our Maintenance 101 guide is a good place to build that foundation.
Pre-Dive Checks: The Non-Negotiable Routine
Every dive on a rebreather begins with a systematic pre-dive check. This is not optional, and it is not something you abbreviate because you ran the same unit yesterday. The pre-dive sequence on an AP Diving unit covers positive and negative pressure tests on the breathing loop, calibration of oxygen sensors, verification of scrubber duration remaining, and confirmation that the electronics, handsets, and bailout systems are functioning correctly.
The positive and negative pressure tests confirm that your loop is sealed. A positive pressure test holds slight overpressure in the loop for a set period to detect leaks at hose connections, counterlung seals, and the mouthpiece. The negative test verifies that the loop can hold a slight vacuum, ensuring no ambient water will infiltrate during the dive. Both tests take only a few minutes but catch the kinds of problems that become emergencies underwater.
Sensor calibration is equally critical. AP Diving units use three independent oxygen sensors to provide redundant PO2 monitoring. During the pre-dive check, you calibrate these sensors against a known gas — typically pure oxygen — and verify that all three readings converge within acceptable tolerances. Any sensor that drifts or responds sluggishly during calibration should be replaced before you dive, no exceptions.
Post-Dive Care: Protecting Your Investment Between Dives
What you do with your rebreather after a dive matters almost as much as what you do before one. At minimum, post-dive care involves removing and properly storing the scrubber canister, thoroughly rinsing the breathing loop and counterlungs with fresh water, and drying all components before storage. Moisture left inside the loop promotes bacterial growth and accelerates corrosion on electronic contacts and sensor faces.
AP Diving recommends disassembling the breathing loop after each dive day — removing hoses, counterlungs, and the mouthpiece assembly — for a complete freshwater rinse. Allow all components to air-dry in a clean, ventilated space before reassembly. The scrubber canister should be emptied after every dive. Partially used absorbent should never be stored inside the canister, as moisture from the spent material will corrode the canister walls and degrade the remaining chemical capacity.
These post-dive habits are straightforward but easy to neglect, especially after a long day on the water. Building them into your routine as non-negotiable steps prevents the kind of slow-onset damage that leads to expensive repairs down the line.
AP Diving’s Recommended Service Intervals
AP Diving structures its maintenance program around three tiers, each designed to catch different categories of wear and degradation before they become safety issues. This tiered approach ensures that routine consumable items are addressed early while deeper inspections happen on a predictable schedule. Tracking your hours is essential — AP Diving’s electronics log dive time automatically, but maintaining your own record of dates, dive counts, and anomalies creates a service history that helps technicians diagnose issues faster.
User-Level Maintenance: Every Dive
This is the tier you own entirely. Pre-dive checks, post-dive cleaning, scrubber management, and oxygen sensor monitoring fall into this category. You perform these tasks every time you use the unit, without exception. Consistency here is what separates divers who get years of reliable service from their units and those who face avoidable failures.
Periodic Inspections: Every 100 Hours or Six Months
At the six-month or hundred-hour mark — whichever comes first — you should conduct a more detailed visual inspection of the entire unit. This includes examining counterlungs, hoses, and mouthpiece assemblies for wear, cracking, or delamination. All user-serviceable O-rings should be inspected and replaced where specified by AP Diving’s maintenance manual. Verify that the ADV and manual add valve function smoothly and respond at their designed cracking pressures.
Annual Service: Full Factory-Level Inspection
Once per year, the unit goes to an authorized service center for a comprehensive teardown and evaluation against factory specifications. This is the deepest level of inspection your rebreather will receive, and it is not something that can be replicated at home. We cover exactly what happens during this service in detail below.
Oxygen Sensors: Lifespan, Replacement, and Signs of Degradation
Oxygen sensors are consumable components with a finite lifespan. The galvanic cells used in AP Diving units typically last twelve to eighteen months under normal use, though environmental factors like temperature, humidity, and storage conditions can shorten that window. AP Diving recommends replacing all three sensors simultaneously at the annual service to maintain matched performance across the voting logic.
Current output at calibration: A healthy sensor produces a millivolt reading within the specified range when exposed to pure oxygen at surface pressure. As the cell ages, its output declines. When a sensor’s millivolt output at calibration drops below the manufacturer’s minimum threshold, it must be replaced regardless of its calendar age. Response time: A degrading sensor responds more slowly to changes in PO2. During calibration, watch how quickly each sensor reaches its final reading — a sensor that lags noticeably behind the other two is nearing end of life. Drift between dives: If a sensor’s reading shifts significantly between pre-dive calibrations without an obvious environmental cause, that sensor should come out of service immediately.
Never ignore a sensor anomaly and assume the other two will compensate. The voting algorithm in AP Diving’s electronics is designed to identify and exclude a single outlier, but that safety margin only works if the remaining two sensors are healthy. Running with a known-degraded sensor eliminates your redundancy entirely. Fresh sensors are inexpensive compared to the safety they provide — stock spares in your kit bag and replace at the first sign of trouble.
Scrubber Canister: Cleaning, Inspection, and Replacement Criteria
The scrubber canister is where your exhaled carbon dioxide is chemically removed from the breathing loop. AP Diving’s radial scrubber design is efficient and predictable, but the canister itself requires regular attention beyond simply refilling it with fresh absorbent. After every dive, empty the spent material completely and inspect the canister interior for signs of corrosion, moisture damage, or absorbent channeling.
Canister body: Look for discoloration, pitting, or any deformation that could create gaps in the absorbent bed. Even small channels allow CO2 to bypass the chemical reaction and reach your breathing gas unfiltered. O-rings and seals: The canister’s sealing surfaces must be clean, undamaged, and properly lubricated with oxygen-compatible grease. A compromised seal can allow loop gas to bypass the scrubber entirely. Mesh screens and spacers: These components keep the absorbent packed uniformly inside the canister. Replace any screen that is torn, corroded, or deformed.
AP Diving specifies a maximum number of operating hours for each canister before mandatory replacement, and your annual service will include a detailed assessment. Between services, if you notice any physical damage or the canister fails to seat properly in the unit, replace it immediately. Scrubber failure is one of the most dangerous rebreather malfunctions — and also one of the most preventable through basic inspection discipline.
Counterlung and Hose Inspection: What to Look For
Counterlungs endure significant mechanical stress over their service life. Each breathing cycle inflates and deflates the bags, flexing the material thousands of times per dive. Over time, this repetitive loading can cause fatigue cracking at fold points, delamination of internal coatings, and weakening of the bonded seams where hoses and fittings attach. During your periodic inspections, inflate each counterlung fully and examine every surface under good light. Pay particular attention to the areas around hose connections and the corners where the material folds during packing.
Breathing hoses: Inspect the corrugated hoses for cracks, kinks, or hardening of the material. Flex each hose through its full range of motion and check for any restriction in airflow. The internal bore should be smooth and free of deposits or biological growth. Mouthpiece assembly: The dive/surface valve is a critical safety component that isolates your breathing loop from the ambient environment. Verify that it switches cleanly between positions, seals completely in surface mode, and shows no sign of cracking around the bite tabs or lever mechanism. AP Diving supplies rebuild kits for the mouthpiece assembly — a cost-effective way to refresh this high-wear component between annual services.
Annual Factory Service: What Happens and Why It Matters
The annual service is the most comprehensive inspection your rebreather will receive. At an authorized service center, trained technicians disassemble the unit down to individual components and evaluate every subsystem against AP Diving’s factory specifications. This includes hydrostatic testing of pressure vessels, electronic diagnostics on the controller and solenoid systems, leak testing of every junction in the breathing loop, and replacement of all consumable items — oxygen sensors, O-ring kits, mouthpiece components, and any parts that show wear beyond acceptable tolerances.
The solenoid valve, which controls oxygen injection into the loop, receives particular attention during the annual service. Technicians verify its response time, check the seat for wear, and confirm that it seals completely when de-energized. A solenoid that leaks oxygen into the loop when closed can create a dangerously hyperoxic mix over time — a fault that may not be apparent during normal pre-dive checks but becomes immediately evident under the controlled conditions of a bench test.
Annual service costs vary depending on the age and condition of the unit, but you should budget approximately $500 to $800 for a standard Inspiration or Evolution service, plus the cost of any replacement parts beyond the standard consumable kit. This investment is modest relative to the value of the equipment and the safety margin it restores. As we discuss in our guide to rebreather safety, no amount of personal skill compensates for a unit that has not been professionally inspected on schedule.
DIY Maintenance vs Professional Service: Where to Draw the Line
AP Diving’s modular architecture is deliberately designed to empower owners. You can and should perform your own pre-dive checks, post-dive cleaning, oxygen sensor replacements, scrubber management, and periodic visual inspections. These tasks are well within the capability of any trained rebreather diver, and performing them yourself deepens your understanding of how the unit works — knowledge that makes you a safer and more confident diver underwater.
The line between DIY and professional service is drawn at anything that requires specialized tools, calibrated test equipment, or access to factory service bulletins. Pressure testing, solenoid diagnostics, electronics firmware updates, and any repair involving the unit’s pressure-rated components should be performed by an authorized technician. Attempting these tasks without proper training and equipment risks introducing faults that are difficult to detect during standard pre-dive checks and may only reveal themselves at depth.
When in doubt, err on the side of professional service. A quick call or email to a service team can help you determine whether an issue is something you can address at home or whether the unit should come in for hands-on inspection. It is always better to ask the question than to take an unnecessary risk with life-support equipment.
Silent Diving’s Service Center and Dealer Network
As the exclusive AP Diving distributor for the Americas, Silent Diving operates a dedicated service center staffed by factory-trained technicians with more than twenty years of experience on the Inspiration and Evolution platforms. Every annual service we perform follows AP Diving’s factory protocols, uses genuine AP Diving parts, and is documented in a service record that travels with the unit for its entire operational life. Our team has seen virtually every configuration and condition these units can present, and that depth of experience translates directly into thorough, reliable service work.
We also coordinate with a network of sixteen authorized dealers across the Americas who stock consumable items — oxygen sensors, absorbent, O-ring kits, and mouthpiece rebuild components — so you can keep your unit maintained between annual services without waiting on international shipping. Many of our dealers also offer local support for periodic inspections and troubleshooting, giving you a nearby resource when questions come up between visits to our Service Center.
Whether your unit is due for its annual service, you have noticed something during a pre-dive check that does not look right, or you simply want guidance on maintaining your equipment between dives, we are here to help. Reach out to our service team to schedule your next appointment or talk through any maintenance question you have. Keeping your rebreather in peak condition is not just what we do — it is a responsibility we share with every diver who trusts their life to a closed-circuit system, and we take it seriously every time a unit comes through our door.
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