Inogen portable oxygen concentrators pull in regular room air, remove the nitrogen, and deliver concentrated oxygen through a nasal cannula. Since ambient air is about 78% nitrogen and only 21% oxygen, the device’s core job is stripping away that nitrogen to produce air that’s roughly 90% or more oxygen. It does this without storing compressed oxygen, which is what makes the device portable and eliminates the need for tank refills.
How Air Becomes Medical-Grade Oxygen
The process inside an Inogen unit is called pressure swing adsorption, or PSA. A small compressor draws ambient air into the device and pressurizes it, then pushes that pressurized air through a filter column packed with a mineral called zeolite. Zeolite is a molecular sieve, a material with tiny, uniform pores that attract and trap nitrogen molecules while letting oxygen molecules pass through. Under high pressure, the zeolite grabs nitrogen. The remaining gas, now heavily concentrated with oxygen, flows out the other side and into a small reservoir ready for you to breathe.
The second half of the cycle is what makes this sustainable. Once a zeolite column is saturated with nitrogen, the pressure drops and the trapped nitrogen is released back into the surrounding air as harmless exhaust. The column is now “clean” and ready to filter again.
Why There Are Two Sieve Beds
Inogen concentrators contain two zeolite columns rather than one. While one column is actively filtering nitrogen out of incoming air, the other is depressurizing and venting the nitrogen it already captured. Every few minutes, the two columns automatically swap roles. This back-and-forth cycle means the device never has to pause: there’s always one column producing oxygen and one column resetting itself. The process runs continuously for as long as the unit is powered on.
Over time, zeolite columns lose efficiency. Inogen recommends replacing the column pair in its home units every 12 months, though operating conditions can shorten that window. The device displays an alert when replacement is due.
Pulse Dose Delivery vs. Continuous Flow
Most portable Inogen models deliver oxygen in pulse doses rather than a continuous stream. Instead of flowing oxygen nonstop, the device uses a sensor to detect the moment you begin inhaling and releases a measured burst of oxygen timed to that breath. This is efficient because oxygen delivered during exhalation is largely wasted, so skipping that phase stretches the device’s battery life and reduces how hard the compressor has to work.
A clinical crossover study published in Respiratory Medicine compared pulse dose concentrators against continuous flow oxygen in patients with COPD during standardized walking tests. Average oxygen saturation levels were similar across delivery methods: 90% with continuous flow, 89% with a pulse dose liquid oxygen device, and 90% with a pulse dose concentrator. However, about 20% of patients showed meaningfully lower oxygen levels (a drop of 4% or more) when using a pulse dose device. Patients using the portable concentrator also needed a higher flow setting (level 4.4 on average) compared to continuous flow (2.9 liters per minute) to achieve the same result. This is why your prescribing provider may set your pulse dose level higher than your continuous flow rate and verify your saturation on the specific device you’ll be using.
Battery, Weight, and Noise
Because the compressor and sieve beds are miniaturized, portable Inogen units weigh between roughly 3 and 5 pounds depending on the model. The Inogen One G5, one of the more popular models, produces about 37 decibels of sound at flow setting 2, which is quieter than a whispered conversation. Battery life varies by flow setting and battery size, but a single battery typically lasts a few hours. Higher flow settings cycle the compressor more frequently, draining the battery faster.
You can also run the unit from a wall outlet or a car’s DC power adapter, which charges the battery while simultaneously producing oxygen. For longer outings, carrying a spare battery extends your time away from a power source.
Using Inogen on Flights
Portable oxygen concentrators that meet FAA requirements are permitted on commercial aircraft, and Inogen models carry that approval. The FAA requires passengers who depend on a concentrator during flight to carry enough spare batteries in their carry-on luggage to last the entire trip, including any layovers or unexpected delays. Spare batteries need to be individually protected from damage and short circuits, typically by keeping the terminal contacts covered or storing each battery in its own bag.
Airlines may have their own additional policies on top of the FAA baseline, so checking with your carrier before booking is worth the few minutes. Most airlines ask for advance notice (often 48 hours) and may request a copy of your oxygen prescription.
What the Device Does Not Do
An Inogen concentrator supplements your breathing, but it doesn’t force air into your lungs the way a ventilator or CPAP machine does. It simply enriches the oxygen content of the air you inhale on your own. It also doesn’t generate oxygen from nothing. It needs access to ambient air, so blocking the intake vents (with blankets, cushions, or tight enclosures) can reduce output or trigger an alarm. Keeping the device in an open, ventilated space ensures the compressor can pull in enough air to maintain oxygen purity.