Luna G3 CPAP Review: Is It Worth It?

What Is the Luna G3?

The Luna G3 is an auto-titrating CPAP (AutoCPAP) machine manufactured by BMC Medical and distributed in the United States primarily by React Health under the Luna brand. The physical device is identical to the BMC G3 A20 sold in international markets. The Luna G3 ships with different firmware versions that write different SD card formats. CPAP Clarity has been verified against contributor data on G3-2.SC.73.04, G3-2.00.77, and G3-2.11.02.33.

BMC Medical is the same company behind the BMC E-20A, the machine commonly supplied through UK rental programs like Intus Healthcare. The Luna G3 sits above the E-20A in the product line. It offers a similar set of therapy features but a more modern internal architecture.

For most users, the Luna G3 does the core job well: it automatically adjusts pressure throughout the night to keep the airway open, logs your therapy data to an SD card, and supports comfortable exhalation relief via Reslex (BMC's equivalent of ResMed's EPR).

The challenge has been reading the data. The Luna G3's SD card format is proprietary and, until now, unsupported by any free web-based tool. CPAP Clarity now reads it directly in your browser. See what CPAP Clarity shows for the Luna G3.

What the Luna G3 Records

Every night, the Luna G3 writes waveform data and event records to its SD card. Here is what CPAP Clarity can decode from that data.

Therapy pressure: One pressure reading per second across the night, so you can see how the AutoCPAP algorithm responded to events.

Leak rate: One reading per second, in liters per minute. Leak is one of the most actionable metrics in your data: high leak means your mask is not sealing properly, which reduces therapy effectiveness.

Obstructive apneas: Complete breathing pauses caused by airway collapse, with timestamps.

Central apneas: Breathing pauses where the brain does not send the drive signal to breathe, with timestamps.

Hypopneas, unclassified apneas, and RERAs: Partial airflow reductions, events the firmware could not classify, and respiratory-effort-related arousals. All three are decoded from the card's event log, with counts verified night by night against OSCAR's reading of a contributor's card.

Machine settings: Therapy mode, pressure range, mask type, tube type, and ramp time when it is not set to auto. Reslex level and humidity are not shown; see the data guide for why.

Session timeline: Each night's session with start time, end time, and usage duration.

What it does not record

Some of these are boundaries in the format itself; others are things we have not been able to verify well enough to display. The difference is named in each case, because "the machine does not record it" and "we cannot read it yet" are different claims and only one of them is ours to make.

Per-second respiratory rate: Not present in the waveform files of the legacy G3-2.SC.73 firmware in any identifiable encoding. The newer G3-2.11.x family does not store a rate either, but it writes a per-breath event log, and CPAP Clarity works your respiratory rate out from that.
Tidal volume and minute ventilation: Not shown. On the newer G3-2.11.x firmware the breath-by-breath flow signal IS on the card, but converting it into calibrated millilitres needs manufacturer-app figures to check against that no contributor has been able to supply. On the older firmware the reserved positions hold zero or non-physiological values. A gap on our side, in other words, not junk on the card.
Flow limitation index: Not shown. The event log holds a couple of codes that may be flow-limitation flags, but nothing has confirmed what they are.
Snore index and Cheyne-Stokes respiration: Not shown. We have not found a channel in this card that we can stand behind for either, which is not the same as saying your machine does not record them. Of the devices CPAP Clarity reads, only ResMed's expose a CSR detection we display.

If you are coming from a ResMed AirSense 11 and are accustomed to seeing respiratory rate, tidal volume, and flow limitation curves, expect tidal volume and flow limitation to show "no data" on the Luna G3 dashboard; respiratory rate appears only on the newer G3-2.11.x firmware family, where it is worked out from the breath-by-breath record on the card. The absence of those channels does not mean your therapy is failing. AHI, pressure, and leak are the primary metrics for evaluating treatment effectiveness.

How to Read Your Luna G3 Data

Everything the machine records goes to the SD card in the back of the unit, at the humidifier end. Power the Luna G3 off, push the card in to release it, put it in your computer or phone, and drop the whole card onto CPAP Clarity. Your AHI, event breakdown, pressure trace, leak, and machine settings appear in a few seconds, on your own device, with nothing uploaded.

The card keeps a short rolling window of detailed data, roughly ten nights on the current firmware, though the nightly summaries reach back much further. Import every week or two if you want to keep the detail.

For the full walkthrough, including what each number means, which channels this machine does not record and why, and how to read the pressure trace against your events, see the Luna G3 data guide.

Luna G3 Settings Explained

CPAP Clarity reads most of your machine settings directly from the SD card. Here is what each one means.

Mode: AutoCPAP means the machine adjusts pressure automatically throughout the night based on detected events.
Pressure range (min/max): In AutoCPAP mode, the machine operates between these two values. Your provider sets these based on your titration results.
Ramp time: The machine starts at a lower pressure and increases to your treatment level over this period, making it easier to fall asleep. A 15-minute ramp is common. CPAP Clarity reads it from the card unless it is set to auto, which carries no fixed duration.
Reslex and humidity: Both are set on the machine, and both are absent from CPAP Clarity. The only place they appear on the card is a factory-defaults block, which reported settings two contributors were not actually using, so we stopped reading it. Higher humidity reduces dryness but can cause condensation in the hose, known as rainout.
Mask type: Tells the machine whether you are using a nasal, nasal pillow, or full face mask. This affects how the machine interprets leak measurements.
Tube type: The Luna G3 supports both a 22mm standard heated tube and a 15mm slim heated tube. The tube type is recorded in your settings.

All of these settings are prescribed by your sleep physician or configured by your provider. If something feels off about your therapy, bring your CPAP Clarity data to your next appointment.

Accessories and Essentials

The Luna G3 uses standard CPAP fittings, so most universal accessories are compatible. You do not need Luna-branded or React Health-branded replacements for most items.

Masks

Your mask determines your comfort and seal quality. The Luna G3 works with any standard CPAP mask. If you are unsure which type suits you, see full face vs. nasal masks or best masks for side sleepers.

Common mask types that work with the Luna G3:

Nasal pillow masks for minimal contact and less claustrophobia
Nasal masks for a balance of seal and comfort
Full face masks if you breathe through your mouth

SD cards and readers

The Luna G3 uses a standard SD card. Any name-brand card up to 32 GB works. See best SD card for your CPAP for specific recommendations.

If your computer lacks a built-in reader, a USB-C SD card reader is an inexpensive addition.

Cleaning and maintenance

Standard CPAP cleaning practices apply to the Luna G3. Clean the mask cushion daily with mild soap, replace filters on schedule, and clean the humidifier chamber weekly.

Helpful supplies:

CPAP cleaning wipes for quick daily mask maintenance
Replacement filters (check your Luna G3 manual for the correct size)
CPAP hose if yours needs replacing

For a complete maintenance routine, see how to clean your CPAP.

Luna G3 vs BMC E-20A vs ResMed AirSense 11

Feature	Luna G3	BMC E-20A	ResMed AirSense 11
Manufacturer	BMC Medical (React Health dist.)	BMC Medical	ResMed
Type	AutoCPAP	AutoCPAP	AutoCPAP
Pressure relief	Reslex (3 levels)	Reslex (3 levels)	EPR (3 levels)
Data channels	Pressure, leak, RR (derived, newer firmware)	Pressure, leak, RR, TV, MV, I:E	Pressure, leak, RR, TV, MV, flow limit, snore
AHI event breakdown	OSA, CSA, HYP, UA	OSA, CSA, HYP	OSA, CSA, HYP, UA
Companion app	PAP Link (optional)	None	myAir
SD card data	Yes	Yes	Yes
CPAP Clarity support	Yes	Yes	Yes

The key data difference is per-second respiratory physiology: the BMC E-20A exposes respiratory rate, tidal volume, minute ventilation, and I:E ratio. The Luna G3's newer firmware generation exposes respiratory rate, derived from the breath-by-breath log on the card, but not tidal volume, minute ventilation, or I:E ratio. The ResMed AirSense 11 adds flow limitation and snore detection on top of that.

For most users evaluating their therapy, AHI, leak, and pressure are the primary metrics. All three devices provide those. The Luna G3 is a capable AutoCPAP machine, and CPAP Clarity gives you access to every data channel the firmware exposes.

The Luna G3 is also closely related to the BMC G3 A20, which uses older firmware and is supported through CPAP Clarity's existing BMC parser. If you are unsure which device you have, check the firmware version in your machine's settings menu or on the label on the bottom of the unit. For a broader comparison including Lowenstein Prisma Smart and Philips, see our CPAP machine comparison.

When to Talk to Your Doctor

Your therapy data is most valuable when you share it with your sleep physician. Patterns worth bringing to your next appointment:

AHI consistently above 5.0 events per hour, the mark the AASM associates with well-controlled CPAP in its in-lab titration guideline. What to do about it is a prescribing decision, so bring the trend rather than a conclusion.
A significant increase in central apneas. Central events do not respond the way obstructive events do. Your provider needs to know about this pattern.
Elevated or rising leak trends despite trying different mask fits or headgear adjustments. You may need a different mask type or size.
Persistent daytime sleepiness despite consistent nightly use and good AHI. Other factors may be affecting your sleep quality.

CPAP Clarity generates PDF therapy reports formatted for your provider to review. Download one before your appointment. Concrete numbers lead to better conversations than general impressions. For tips on presenting your data effectively, see preparing CPAP data for your doctor.

Frequently Asked Questions

Is the Luna G3 the same machine as the BMC G3 A20?

Physically, yes. BMC Medical builds both, and React Health distributes the same hardware in the United States under the Luna brand while it sells internationally as the BMC G3 A20. What differs between individual units is firmware, and firmware is what decides the SD card format. CPAP Clarity has been verified against contributor cards on G3-2.SC.73.04, G3-2.00.77, and G3-2.11.02.33.

Can OSCAR read a Luna G3 card?

Only OSCAR 2.0 and later. Stock OSCAR 1.7.2 and earlier cannot open this family at all, which is why plenty of Luna owners were told their card was unreadable; OSCAR 2.0, released in June 2026, added a loader for it. That newer loader is what the numbers here were checked against, night by night, which is the cross-check every CPAP device on this site has to pass before it ships.

What does the Luna G3 not record?

Four things people go looking for and will not find: per-second respiratory rate, tidal volume, minute ventilation, and a flow limitation index. The reasons differ. The newer G3-2.11.x firmware writes a per-breath event log, so CPAP Clarity works your respiratory rate out from that, while the legacy G3-2.SC.73 firmware does not carry it in any form we can identify. Tidal volume and minute ventilation are a gap on our side rather than the card's: the newer firmware does write a flow signal, but converting it into calibrated millilitres needs manufacturer figures to check against that no contributor has been able to supply. And the event log holds a couple of codes that may be flow-limitation flags, but nothing has confirmed what they are.

Does the Luna G3 separate obstructive and central apneas?

Yes. Unlike some machines in this price range, the Luna G3 logs obstructive apneas, central apneas, hypopneas, unclassified apneas and RERAs as distinct timestamped events, so your AHI breaks down by type rather than arriving as one number.

What SD card does the Luna G3 take?

A standard full-size SD card. Any name-brand card up to 32 GB works, and no adapter is needed. If your computer has no built-in reader, an inexpensive USB SD card reader is all you need.

What is Reslex?

Reslex is BMC's exhalation relief, the same idea as ResMed's EPR: the machine drops pressure slightly as you breathe out so exhaling against therapy pressure feels less like work. Your level is set on the machine, and CPAP Clarity does not display it, because the only place it appears on the card turned out to be a factory-defaults block rather than your real configuration.

Get Started

If you have a Luna G3 and have never seen your detailed therapy data, now you can. Pull your SD card, open cpapclarity.com, and drop in the folder. It takes under a minute, it is completely free, and your health data stays on your device.

Analyze your Luna G3 data now, free and private →