What Is a Non-Rebreather Mask? A Plain-Language Guide

Last verified: October 6, 2026. A non-rebreather mask is a face mask with an attached reservoir bag and a set of one-way valves, designed to deliver a high concentration of oxygen to a person who is breathing on their own. It is a common sight in emergency departments, ambulances, and hospital wards, and it is usually used for short-term, higher-need oxygen delivery rather than long-term home use. This guide explains what a non-rebreather mask is, how it works in general terms, how it differs from other oxygen devices, and what supply teams should know.

This page is general information, not clinical or safety training. Always follow your institution’s procedures and the manufacturer’s instructions for any device.

What Is a Non-Rebreather Mask?

A non-rebreather mask (often shortened to NRB or NRBM) is an oxygen delivery interface that covers the nose and mouth and is fed by a flow of oxygen from a wall outlet or cylinder. It has three main features that set it apart from a simple oxygen mask: a soft reservoir bag attached below the mask, a one-way valve between the bag and the mask, and one-way valves over the side openings of the mask.

The name describes the intent. The valves are arranged so that the person breathes in oxygen from the reservoir and breathes out through the side valves into the room, so that very little of the exhaled air is breathed back in. That keeps the oxygen concentration the person inhales as high as the mask design can achieve without a tight-sealing system.

How a Non-Rebreather Mask Works, in General Terms

1. Oxygen flows from the source through tubing and into the reservoir bag, where it collects between breaths.
2. When the person breathes in, a one-way valve opens and lets oxygen from the bag flow into the mask. The side valves on the mask close, or are covered, so that room air does not freely enter.
3. When the person breathes out, the valve between the mask and the bag closes so exhaled air does not go back into the bag, and the side valves open to let it escape.

Because the bag has to stay inflated enough to supply each breath, the oxygen flow into the mask is set high enough to keep the reservoir from collapsing, and the mask needs to fit snugly enough to work as intended. The exact flow and fit that are appropriate are decisions for the clinical team and the manufacturer’s instructions.

Note that many masks include a safety feature: one of the side valves is sometimes left without a flap or is designed so that if the oxygen supply fails, the person can still draw in room air. Designs vary by manufacturer, so use the product’s own instructions rather than assuming how a particular mask is built.

Why Non-Rebreather Masks Exist

Some situations call for delivering oxygen at a higher concentration than a nasal cannula or a simple mask can achieve, but do not yet require a ventilator or advanced airway. A non-rebreather mask fills that role. It can be set up quickly, requires no machine other than an oxygen source, and gives the clinical team a way of increasing oxygen delivery while they assess and treat the cause. That speed and simplicity are why it is widely stocked in emergency and acute-care settings.

Who Uses a Non-Rebreather Mask

Non-rebreather masks are used by paramedics and emergency medical services, emergency department and hospital ward staff, and in some outpatient and urgent-care settings. They are generally used for people who are breathing spontaneously but need a high concentration of oxygen for a limited period, for example during acute illness or injury, or while a more definitive treatment plan is being arranged. Decisions on who needs one, for how long, and at what flow are made by trained clinicians. This is not a home-use device in the sense that a concentrator and cannula are.

Types and Variations

Non-rebreather masks are broadly similar, but there are some differences worth knowing:

• Size: adult, pediatric, and sometimes infant sizes are available, with different mask and bag volumes.
• Material: most are made of soft, clear plastic so that the face and any vomit or secretions are visible. Some are latex-free by design.
• Fit features: adjustable elastic head straps and a flexible metal nose clip help the mask conform to the face.
• Tubing: most include a length of oxygen supply tubing with a standard connector, though some are sold without tubing.
• Valve design: the arrangement of side valves and safety features differs by manufacturer.

How a Non-Rebreather Mask Differs from Related Devices

• Non-rebreather vs. simple face mask. A simple mask lacks the reservoir bag and one-way valves, so exhaled air and room air mix more freely, and the oxygen concentration delivered is lower. It is used where a moderate boost is needed.
• Non-rebreather vs. partial rebreather mask. A partial rebreather has a reservoir bag but no one-way valve between the bag and mask, so a portion of exhaled air passes back into the bag. The design is similar in appearance but intended for slightly different concentrations.
• Non-rebreather vs. nasal cannula. A nasal cannula is lighter and more comfortable for long-term wear but delivers lower and less predictable concentrations. See our overview of CPAP and oxygen mask types for related mask designs.
• Non-rebreather vs. bag-valve-mask. A bag-valve-mask is a resuscitation device that is squeezed by a rescuer to push air into the lungs of a person who is not breathing adequately. A non-rebreather mask only supplies oxygen to a person who is breathing on their own. The two look somewhat alike but do very different jobs.
• Non-rebreather vs. CPAP or ventilator. Neither of those devices is replaced by an NRB. CPAP and ventilators apply pressure to support the airway or the work of breathing, while an NRB only increases the oxygen content of the air breathed in.

Where You Will See a Non-Rebreather Mask in Practice

The non-rebreather mask tends to appear at points of acute need. Ambulance crews often use it in the field, emergency departments use it during initial assessment, and wards and recovery areas keep it available in case a patient’s condition worsens. It is also a standard item on emergency carts and in resuscitation and rapid-response kits. In many facilities it is treated as a bridge: a way of delivering high-concentration oxygen quickly while the team works out the cause of the problem and decides whether the person can be stepped down to a gentler interface, such as a cannula, or needs more support.

Because the mask depends on a working oxygen source and a properly inflated reservoir, staff training typically emphasizes checking the connection, the supply, and the bag, and monitoring the person’s response with measurements such as blood oxygen readings. Training of this kind is delivered through facility programs and cannot be replaced by a general explainer.

The reservoir bag and valves are also the parts most likely to be misunderstood by non-clinical readers. They are not decorative: the bag is a storage space for oxygen, and the valves control the direction of air. A mask with a damaged bag, a stuck valve, or a poor facial seal will not perform as the design intends, which is a reason to inspect stock for damage and to follow the manufacturer’s instructions.

Practical Relevance for Research Administration and Procurement

Non-rebreather masks are inexpensive single-use items, but they are essential stock for emergency readiness. Several practical considerations apply to people who manage them.

First, availability in a range of sizes is important. Emergency carts, ambulance kits, and ward stock typically need adult and pediatric versions on hand, so supply plans have to cover both. For readiness-oriented reading, see our guide to the crash cart.

Second, packaging and expiry affect stock management. Masks are usually individually packaged and carry date information, so facilities typically rotate stock and track expiry as part of cart and kit checks.

Third, specification matters when substituting products. Valve design, tubing included or not, and connector type can differ between manufacturers, so changing supplier means confirming the replacement fits the facility’s oxygen equipment and training.

Fourth, because the mask is a single-patient device, it is generally discarded after use rather than reprocessed, and usage tracking by unit helps with forecasting. In research settings where the oxygen delivery method is part of a protocol, the specific mask type and setup may need to be recorded and consistently sourced.

Frequently Asked Questions

What is a non-rebreather mask used for?

It delivers a high concentration of oxygen to a person who is breathing on their own, typically for short-term use in emergency or acute-care situations.

Why does a non-rebreather mask have a bag?

The reservoir bag stores oxygen between breaths so that a large share of each breath comes from oxygen rather than room air. The bag needs to stay inflated for the mask to work as designed.

What does non-rebreather mean?

It means the one-way valves are arranged so the person does not breathe back in most of what they just breathed out. Exhaled air leaves through the side valves instead of returning to the bag.

Is a non-rebreather mask the same as a simple oxygen mask?

No. A simple mask has no reservoir bag or one-way valve between the bag and mask, and it generally delivers a lower oxygen concentration.

Do non-rebreather masks come in child sizes?

Yes. Pediatric and sometimes infant sizes are made, with smaller masks and bags. Using the right size matters for fit and for the reservoir to work as designed, and the clinical team selects it.

Can a non-rebreather mask be used for long periods?

It is usually used for shorter periods while the care team assesses the situation, because it is less comfortable than a cannula and ties up the face. How long is appropriate is decided clinically.

Can someone use a non-rebreather mask without training?

Oxygen is a medical therapy, and correct fit, flow, and monitoring matter. Use should follow facility procedures and training, and this guide does not replace either.