Inogen One G4
Key features
- Purity 90-95%
- Type Portable (Battery-powered)
- Pulse Flow 1-3Pulse setting
- Weight 1.27kg
- Oxygen Purity Indicator (OPI) No
- Battery backup (at 2 pulse setting) 2.7hours
Specifications
| Purity | 90-95% |
|---|---|
| Type | Portable (Battery-powered) |
| Pulse Flow | 1-3Pulse setting |
| Weight | 1.27kg |
| Battery backup (at 2 pulse setting) | 2.7hours |
| Recharge time | 3hours |
| Backup with external battery pack | 5hours |
| Sound level | 40db |
| Dimensions | 6.5H x 5.91W x 2.68Dinch |
| Operating altitude | 10000feet |
|---|---|
| Loss of Power Alarm | Yes |
| System Malfunction Alarm | Yes |
| No Flow Alarm | Yes |
| Indian Voltage Model | Yes |
| Company Headquarters | USA |
| US FDA Approved | Yes |
| FAA Approved | Yes |
| CE Certified | Yes |
Pros and cons
PROS
- 1.27 kg published weight is class-leading for FAA-approved pulse portables with full alarm packages
- 40 dB published sound level is within 2 dB of the quietest portables ever made
- Full alarm suite (loss of power, system malfunction, no flow) despite the small form factor
- 5 hours with external battery pack extends the 2.7-hour base runtime meaningfully
CONS
- Stock: Discontinued per manufacturer brochure and e-commerce product listings — parts pathway is closing
- No Oxygen Purity Indicator (OPI) — gap for unattended or travel use
- 1–3 pulse setting range is narrow vs the G5's 1–6 and active competitors' 1–5/1–6
The Inogen One G4 was one of the most successful ultra-light pulse-flow portable concentrators in the Indian market during its active-SKU years — a 1.27 kg unit at indicative retail ₹2,11,200 (varies by region/dealer) that paired FAA approval with a nearly bag-pocket form factor. It is now listed as Discontinued per manufacturer brochure and e-commerce product listings, superseded in Inogen’s line-up by the G5. The G4 carries FDA, FAA, and CE certifications, is an Indian Voltage Model, and has a full alarm package including the no-flow alarm that several peer discontinued portables (Focus, Freestyle 3) lack. It does not have an Oxygen Purity Indicator (OPI), which is the main clinical gap.
What the specs actually mean
Published purity is 90–95% — standard PSA pulse-flow envelope. The G4 does not have an OPI per the published technical details — the field is empty. What it does have is a full set of the alarms that catch real-world failure modes: loss of power, system malfunction, and no flow are all flagged “Yes” in additional details. The no-flow alarm in particular is more valuable than many pulse-only portables offer — it catches cannula blockage or disconnection, a real failure mode during active use.
The 1–3 pulse setting range is the defining prescribing constraint. At setting 2 (the most common home-prescription setting), the G4 delivers an LPM-equivalent of roughly 1 LPM at a 20 breath-per-minute rate. At setting 3, the ceiling is approximately 1.5 LPM equivalent. For patients on the mild pulse-flow end of the prescribing spectrum, the G4 is adequate; for moderate or higher pulse settings, it is under-specced.
Battery backup at pulse setting 2 is published at 2.7 hours from the internal battery and 5 hours with the external battery pack. This is shorter than the G5’s 6.5-hour base and 13-hour extended, reflecting the G4’s smaller battery and lighter form factor. Recharge time is 3 hours.
The 1.27 kg weight is the headline spec. It is one of only two POCs (with the 1 kg Airsep Focus, also Discontinued) that ever broke the 1.5 kg threshold in the Indian market. At 1.27 kg, the G4 is genuinely shirt-pocket-adjacent in a lightweight side bag — unobtrusive for daily urban mobility in a way the 2.3–2.6 kg active-SKU portables are not.
The 40 dB published sound level is close to the class-leading G5 (38 dB) and quieter than the SimplyGo Mini (52 dB) by a meaningful margin. For bedside or shared-space use, 40 dB is below the threshold where portable noise becomes intrusive.
Altitude and certifications
10,000 ft operating altitude covers the full Indian hill-station circuit below Leh, matching the G5 and the SimplyGo Mini. FAA approval is confirmed in published additional details — carry-on legal for most international airlines. FDA, CE and Indian Voltage Model flags are all “Yes.”
Who should buy it
The narrow residual-stock fit: a patient on a mild pulse-flow prescription (setting 1–3 effective) who values extreme lightweight portability, who has access to residual Inogen G4 inventory with written parts-and-service commitments, and who is willing to compensate for the missing OPI with SpO2 monitoring. That patient profile does exist — mobility-limited older adults for whom even 2.3 kg is difficult, osteoporosis patients, or patients whose social context makes visible oxygen equipment a daily barrier.
Patients with post-stroke upper-limb weakness, patients recovering from orthopaedic procedures with activity restrictions, and patients whose employment or social life involves long periods standing or walking all benefit disproportionately from the 1.27 kg weight. For these profiles, the weight differential versus the active-SKU alternatives is not a minor spec variation — it is the difference between a portable that actually gets used daily and one that sits on a shelf because it is too tiring to wear.
For households that want to add a discreet secondary portable to an existing home oxygen setup and are not willing to commit the ₹2,14,999 for an active G5, the G4 at ₹2,11,200 is roughly the same price but with a Discontinued flag. The price similarity to the G5 is striking — the G4 does not offer a discount for its status, which materially reduces its attractiveness versus the active-SKU G5.
If a specific dealer is offering residual G4 inventory at 20–30% below the listed ₹2,11,200 with written service commitments, the 1.27 kg weight may justify the buy for a weight-sensitive patient. At full retail, it generally does not.
Who shouldn’t
Anyone who can use the G5 (₹2,14,999 indicative, In Stock) should buy the G5 instead. The G5 has OPI, 1–6 pulse settings vs G4’s 1–3, 6.5 hour base battery vs G4’s 2.7 hours, 38 dB vs 40 dB, and an active manufacturer warranty. The 1.27 kg vs 2.6 kg weight advantage of the G4 is real, but on every other spec the G5 is meaningfully better.
Anyone whose prescription requires pulse settings 4–6 cannot use the G4 — the 1–3 ceiling is a hard constraint. The G5 or SimplyGo Mini are required.
Anyone for whom OPI is clinically important should not buy the G4. This includes most patients in Indian coastal cities (Mumbai, Chennai, Kolkata, Kochi) where sieve-bed contamination risk is higher, and any patient using the portable for extended unattended periods.
Anyone relying on a strong service network for the long-term life of the machine should not buy a discontinued Inogen portable. Inogen’s India service network is thinner than Philips Respironics and CAIRE, and the G4 being discontinued means parts are increasingly available only from residual manufacturer inventory — battery replacement lead times in India for Inogen portables can stretch to 4–6 weeks.
How it compares to real alternatives
G4 vs Inogen One G5
The direct upgrade path in the Inogen line. G5: 2.6 kg, 1–6 pulse, 6.5 hours at pulse 2, 38 dB, has OPI, full alarm suite, 10,000 ft altitude, 2-year active warranty, ₹2,14,999, In Stock. G4: 1.27 kg, 1–3 pulse, 2.7 hours at pulse 2, 40 dB, no OPI, full alarm suite, 10,000 ft altitude, no active warranty, ₹2,11,200, Discontinued. The G4 is half the weight. The G5 wins on every other spec. Pick the G5 unless weight is the single determining factor — which is rare.
G4 vs Airsep Focus
Both discontinued ultra-light portables. Focus: 1 kg, fixed 17.25 mL dose output, 3 hours at pulse 2, 42 dB, no OPI, no loss-of-power alarm, 10,000 ft altitude, ₹1,63,200. G4: 1.27 kg, 1–3 pulse, 2.7 hours at pulse 2, 40 dB, no OPI, full alarm suite, 10,000 ft altitude, ₹2,11,200. Pick the Focus if fixed single-dose output is clinically adequate and the 270 g weight saving matters; pick the G4 if titratable 1–3 pulse settings are required and the alarm-package difference (loss-of-power plus no-flow) is valued.
G4 vs Airsep Freestyle 3
Another discontinued pulse portable. Freestyle 3: 2 kg, 1–3 pulse, 2.5 hours base / 10 hours extended at pulse 2, 41 dB, no OPI, 12,000 ft altitude, ₹1,58,400. G4: 1.27 kg, 1–3 pulse, 2.7 hours base / 5 hours extended at pulse 2, 40 dB, no OPI, 10,000 ft altitude, ₹2,11,200. Pick the Freestyle 3 for 12,000 ft altitude needs and the longer extended-battery duration at a lower price; pick the G4 for the 730 g weight advantage if altitude above 10,000 ft isn’t needed.
G4 vs SimplyGo Mini
Active SKU comparison. SimplyGo Mini: 2.3 kg, 1–5 pulse, 4.5 hours at pulse 2, 52 dB, has OPI, 10,000 ft altitude, ₹2,10,700, In Stock. G4: 1.27 kg, 1–3 pulse, 2.7 hours at pulse 2, 40 dB, no OPI, 10,000 ft altitude, ₹2,11,200, Discontinued. G4 wins on weight (45% lighter) and sound (12 dB lower). SimplyGo Mini wins on pulse range (1–5 vs 1–3), battery life (4.5 vs 2.7 hours), OPI presence, active warranty, Philips India service network, and active stock. Pick the SimplyGo Mini unless the G4’s weight and sound advantages are specifically load-bearing. The near-identical retail pricing (within ₹500) makes the SimplyGo Mini the stronger value proposition despite the 1.03 kg weight penalty.
Indian-market considerations
The G4 is Indian Voltage Model per published additional details — 220V/50Hz compatible without a step-down transformer. A small inline stabiliser for home AC charging in tier-2 cities with voltage variability is optional.
CDSCO approval status is not stated in the published key features or additional details for this SKU in the data we reviewed (CDSCO Medical Device Registry). Discontinued SKUs frequently have lapsed Indian registration; verify with the dealer.
Inogen India service network is thinner than Philips Respironics, and for discontinued SKUs the gap widens. Battery replacement is the most common portable-unit service event; Inogen batteries in India have historically had 3–5 week lead times for active SKUs, and longer for discontinued models. Before purchasing residual G4 stock, verify in writing: (1) battery availability and price, (2) local service dealer contact, (3) out-of-warranty service turnaround.
Online-vs-hospital channel gap is wide on discontinued portables — hospital channels do not stock them. The G4 is an online-dealer purchase at this point.
For international travel with a G4, the FAA paperwork flow is straightforward — the unit has been on the FAA-approved list since initial certification and Indian airline ground staff recognise the model. Carry the FAA approval letter printout, the manufacturer brochure, and a current prescription at check-in. For domestic Indian flights, Indigo, Vistara, Air India and SpiceJet all accept G4-class portables in the cabin with advance notification (typically 48 hours).
The Indian pre-owned market for the G4 is noteworthy: because the G4 had a long active-SKU run, the pre-owned inventory is larger than for most other discontinued portables. A well-maintained pre-owned G4 from a verified dealer (with battery less than 200 charge cycles) can be a defensible buy at 40–50% of the new-retail figure, subject to the same parts-pathway caveats as new residual-stock inventory. In our editorial review’s view, pre-owned G4 should not be purchased without a functional-test demonstration and a written 30-day return window from the dealer.
Verdict
The Inogen One G4 is a historically well-engineered ultra-light pulse portable whose main niche — sub-1.5 kg weight with a full alarm package — has effectively been vacated without a direct active-SKU replacement. Its discontinued status, absence of OPI, and pricing that is nearly identical to the active-SKU G5 combine to make it a difficult recommendation in 2026.
Score it 6.8 out of 10. Points off for the Discontinued status, the missing OPI, the narrow 1–3 pulse range, and the near-identical pricing to the superior-specced G5. Points on for the 1.27 kg weight, the 40 dB sound level, and the full alarm suite that exceeds many peer discontinued portables. For a weight-sensitive patient on mild pulse settings with verified parts-and-service assurances, the G4 can still be defensible. For almost every other buyer, the active Inogen One G5 is the right choice at a price differential of under ₹4,000.
