Non-rebreather Mask · What Is It, When Is It Used, and More

Published: Oct 22, 2025

Author: Lily Guo, MD•

Editor: Alyssa Haag, MD•

Editor: Emily Miao, PharmD, MD•

Editor: Kelsey LaFayette, DNP, ARNP, FNP-C•

Editor: Anna Hernández, MD

Illustrator: Jessica Reynolds, MS•

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What is a non-rebreather mask?

A non-rebreather mask (NRM) is a non-invasive oxygen supplementation device that is used  in clinical situations where a high concentration of oxygen is urgently needed, typically in a hospital setting.

A non-rebreather mask consists of a face mask that covers the nose and mouth, a reservoir bag, oxygen tubing, and several one-way valves. The mask creates a loose seal over the face to direct high-concentration oxygen into the airway, while the attached reservoir bag stores nearly 100% oxygen that the person inhales with each breath. A one-way valve between the mask and the bag allows oxygen to flow in but prevents exhaled air from entering the bag. Additional side valves let exhaled air out and block room air from entering during inhalation.

Thanks to this setup, non-rebreather masks are able to greatly increase the amount of inspired oxygen compared to normal breathing, nasal cannulas, or simple face masks. For reference, the normal fraction of inspired oxygen (FiO₂), or concentration of oxygen in the air, is approximately 21% at sea level. A non-rebreather mask can increase the FiO₂ to 60–90%, in contrast to simple masks which provide a maximum FiO₂ of 50-60%.

Even though non-rebreather masks deliver high concentrations of oxygen, they don’t provide a precise or consistent FiO₂. That’s because the actual amount of oxygen the individual receives depends on their breathing pattern, mask fit, and oxygen flow rate. For example, in people who are breathing very rapidly or deeply—such as those in respiratory distress—the oxygen flow rate may not be enough to fully meet their breathing demands. When that happens, the person may inadvertently inhale room air around the edges of the mask or through the valves, which reduces the actual FiO₂ delivered.

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When are non-rebreather masks used?

Non-rebreather masks are used in individuals who are still able to breathe on their own but require additional oxygen supplementation to maintain adequate blood oxygen levels. They are commonly indicated in acute situations such as respiratory failure, lung trauma, smoke inhalation, carbon monoxide poisoning, or chronic lung conditions that suddenly worsen. They are also used to deliver high-flow oxygen as a first-line treatment for cluster headache attacks. Because they can quickly deliver a high FiO₂, non-rebreather masks are particularly valuable in emergency settings before more definitive interventions like intubation or transition to a more controlled oxygen delivery system (e.g., Venturi mask or high-flow nasal cannula).

What oxygen flow rate is needed for a non-rebreather mask?

A non-rebreather mask requires an oxygen flow rate of 10 to 15 liters per minute (L/min) to ensure that the reservoir bag does not collapse fully when the individual inspires. If the oxygen flow rate is too low, the individual may inhale some of the exhaled CO₂ from the reservoir, defeating the purpose of the non-rebreather mask.

What is the difference between a non-rebreather mask and a partial rebreather mask?

Both non-rebreather and partial rebreather masks are oxygen delivery devices designed to increase oxygen delivery by using a reservoir bag filled with nearly 100% oxygen. The key difference between them is that the non-rebreather mask has a one-way valve between the mask and the reservoir that prevents any exhaled air from re-entering the bag. In contrast, a partial rebreather mask lacks this valve, allowing some of the exhaled air—particularly from anatomical dead space, which still contains oxygen—to flow back into the reservoir during exhalation. As a result, the individual inhales a mixture of fresh oxygen and a portion of their previously exhaled air, which is why it’s called a “partial” rebreather. The mix of fresh oxygen and rebreathed air results in an FiO₂ that’s higher than a simple face mask but lower than a non-rebreather mask.

What is the difference between a non-rebreather mask and a simple face mask?

The difference between a non-rebreather and a simple face mask is that simple masks aren’t attached to a reservoir and don’t have valves that prevent the inhalation of room air or rebreathing exhaled CO₂. Generally, simple face masks are used when nasal cannulas are unable to provide enough oxygen, but a high concentration of oxygen isn’t needed to correct blood oxygen levels.

What are the most important facts to know about non-rebreather masks?

Non-rebreather masks are used to provide a high concentration of oxygen to an individual who is still capable of breathing on their own. They are particularly useful in cases of lung damage from smoke inhalation, carbon monoxide poisoning, or acute respiratory failure. The mask consists of multiple one-way valves, which prevent exhaled gases such as carbon dioxide from re-entering the reservoir bag, which ensures the individual is only inhaling oxygen supplied to the reservoir bag. The mask is connected to an oxygen tank via a long tube, similar to a simple face mask. The non-rebreather mask allows for a FiO2 of up to 90%, whereas the simple mask has a FiO2 of 50 to 60%. The minimal flow rate of non-rebreather masks is typically 10-15 liters per minute to prevent collapse of the reservoir bag upon inhalation.

Key Takeaways

Definition	A non-rebreather mask (NRM) is a non-invasive oxygen supplementation device that is used in clinical situations where a high concentration of oxygen is urgently needed, typically in a hospital setting.
Mechanism	- Composed of: - Face mask – delivers oxygen into airways - Reservoir bag – stores nearly 100% oxygen to be inhaled - One-way valve between mask and bag – prevents exhaled air from flowing into the bag - Other side valves – block room/exhaled air from entering - Can increase the FiO₂ to 60–90% - Vs simple masks: 50-60% - Don't provide precise or consistent FiO₂, which depends on: - Breathing pattern - Mask fit - Oxygen flow rate
Use	- Individuals who are still able to breathe but require additional oxygen supplementation - Indicated in: - Respiratory failure - Lung trauma - Smoke inhalation - Carbon monoxide poisoning - Chronic lung conditions that suddenly worsen - Cluster headache attacks - Emergency settings before intubation or transition to other oxygen delivery systems
Oxygen Flow Rate	- Requires oxygen flow rate of 10 to 15 liters per minute - If too low → exhaled CO₂ may be re-inhaled from the reservoir
Non-Rebreather Mask vs Partial Rebreather Mask	- Non-rebreather: has a one-way valve between mask and reservoir - Partial rebreather: no valve → some of the exhaled air flows into the reservoir → mix of fresh oxygen and exhaled air → lower FiO₂
Non-Rebreather Mask vs Simple Face Mask	- Simple masks: - Not attached to reservoir - No valves - Used when a high concentration of oxygen is not required

References

Batool S, Garg R. Appropriate use of oxygen delivery devices. Open Anesthesiol J. 2017;11(1):35-38. doi:10.2174/1874321801711010035

Hardavella G, Karampinis I, Frille A, Sreter K, Rousalova I. Oxygen devices and delivery systems. Breathe (Sheff). 2019;15(3):e108-e116. doi:10.1183/20734735.0204-2019

Kramer D, Baram M. Non-rebreather mask: A bridge worth crossing? Am J Med Sci. 2021;361(4):409-410. doi:10.1016/j.amjms.2021.01.011

Parry A. Understanding the use of oxygen delivery devices. Nurs Stand. 2023;39(3):77-82. doi:10.7748/ns.2023.e12175