Shopping for a portable oxygen concentrator, you'll quickly run into two terms: continuous flow and pulse flow. They sound similar, but they work differently and suit different parts of your day. This guide explains how an oxygen concentrator works, what separates the two types, and how to think about which one fits your life.

How does an portable oxygen concentrator work?

The air around us is roughly one-fifth oxygen, with most of the rest being nitrogen. An oxygen concentrator doesn't store oxygen in a tank. It makes concentrated oxygen from the room air, in a few steps:

1. It draws in air through an intake, where a filter element keeps out dust and particles.
2. It compresses the air and sends it through a bed of material called a molecular sieve.
3. The sieve bed captures nitrogen, letting concentrated oxygen pass through.
4. The oxygen is delivered to you through a nasal cannula, while the captured nitrogen is released back into the air.

Machines typically use more than one sieve bed, taking turns so that oxygen is produced steadily. Because the sieve and the filter do so much of the work, they are the two parts that need regular replacement. We cover that in our guide to maintaining your portable oxygen concentrator.

Two ways to deliver oxygen

The difference between continuous and pulse flow isn't how the oxygen is made. It's how the oxygen machine delivers it to you.

Continuous flow delivers a steady stream of oxygen at the rate you set, all the time, whether you breathe in or out. The flow is measured in liters per minute (L/min).

Pulse flow (also called pulse dose or on-demand) senses when you start to inhale and delivers a burst of oxygen at that moment. It doesn't run when you exhale. Because it delivers oxygen only when needed, a pulse machine can be smaller and lighter.

Continuous vs. pulse at a glance

• Delivery: continuous gives a constant stream; pulse gives a burst with each detected breath.
• Depends on your breathing: continuous doesn't; pulse does, because it needs to detect your inhale.
• Settings: continuous is set in liters per minute; pulse uses setting numbers, such as 1 to 8 on our pulse model.
• Size and portability: pulse machines are generally built for mobility; continuous machines deliver steady flow with a design focused on higher output.
• Best time of day: continuous is well suited to night as well as day; pulse is best used during the day.

An important note: pulse settings are not liters per minute

Many people assume that a pulse setting of 2 equals 2 liters per minute. It doesn't. Pulse settings describe the amount of oxygen delivered with each breath, and they're a different measurement from continuous flow. That's why you can't directly compare a pulse setting with a continuous flow rate. 

Why continuous flow suits nighttime use

When you sleep, your breathing changes. It becomes slower and shallower, and many people breathe through their mouth. A continuous machine isn't affected by any of this, because it delivers oxygen steadily without needing to detect your breath. That makes it a good fit for the night.

That's why our continuous-flow model is designed so one machine can go with you through the day and stay beside you through the night.

Why pulse flow is best for daytime

A pulse machine relies on detecting your inhale. When you're awake and moving around, that works well, and the compact design makes pulse machines easy to carry for walks, errands and travel. During sleep, though, breathing patterns, especially mouth breathing, can be harder for the machine to detect. For that reason, we recommend using a pulse machine during the day only.

Which type fits your life?

Here's a simple way to think about it, along with questions to bring to your doctor:

• If you need oxygen at night, a continuous-flow machine is the better choice.
• If you need higher flow, ask your physician whether continuous flow is right for you. Our continuous model delivers up to 1.6L.
• If you need oxygen mainly when you're out and about, a pulse machine may suit your routine.
• If you want one machine for everything, a continuous-flow machine can serve both day and night.
• If you want the best of both, many people use a continuous machine for night and home, and a pulse machine for daytime trips.

Questions to ask yourself:

• Do I need continuous flow, pulse flow, or both?
• What flow rate or setting should I use at rest, during activity and during sleep?
• Is a pulse machine suitable for my breathing pattern?

Our high-flow lineup

We focus on high-flow portable oxygen concentrators, because we found that most machines on the market are 1L pulse models and many customers needed more.

• Continuous-flow model: up to 1.6L of steady flow, suited to day and night.
• Pulse-flow model: 8 settings (1–8), built for daytime mobility.
• Both models: only 6.6 lbs (3 kg), three ways to power (adapter, car charger and battery), a replaceable molecular sieve and a complete accessory kit in the box.
• Backed by free shipping on U.S. orders over $129, 30-day returns and a 2-year limited warranty.

Not sure which one is right for you? Call us toll-free at 1-(877) 767-8699 or email support@portableoxygenshop.com. Our calls are answered by real people. We can explain the differences between our models.